[PATCH v2 0/6] Speed up mremap on large regions

[PATCH v2 0/6] Speed up mremap on large regions

[Kalesh Singh]

This version 2 of the mremap speed up patches previously posted at:
https://lore.kernel.org/r/20200930222130.4175584-1-kaleshsingh@google.com

mremap time can be optimized by moving entries at the PMD/PUD level if
the source and destination addresses are PMD/PUD-aligned and
PMD/PUD-sized. Enable moving at the PMD and PUD levels on arm64 and
x86. Other architectures where this type of move is supported and known to
be safe can also opt-in to these optimizations by enabling HAVE_MOVE_PMD
and HAVE_MOVE_PUD.

Observed Performance Improvements for remapping a PUD-aligned 1GB-sized
region on x86 and arm64:

    - HAVE_MOVE_PMD is already enabled on x86 : N/A
    - Enabling HAVE_MOVE_PUD on x86   : ~13x speed up

    - Enabling HAVE_MOVE_PMD on arm64 : ~ 8x speed up
    - Enabling HAVE_MOVE_PUD on arm64 : ~19x speed up

          Altogether, HAVE_MOVE_PMD and HAVE_MOVE_PUD
          give a total of ~150x speed up on arm64.

Changes in v2:
  - Reduce mremap_test time by only validating a configurable
    threshold of the remapped region, as per John.
  - Use a random pattern for mremap validation. Provide pattern
    seed in test output, as per John.
  - Moved set_pud_at() to separate patch, per Kirill.
  - Use switch() instead of ifs in move_pgt_entry(), per Kirill.
  - Update commit message with description of Android
    garbage collector use case for HAVE_MOVE_PUD, as per Joel.
  - Fix build test error reported by kernel test robot in [1].

[1] https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org/thread/CKPGL4FH4NG7TGH2CVYX2UX76L25BTA3/

Kalesh Singh (6):
  kselftests: vm: Add mremap tests
  arm64: mremap speedup - Enable HAVE_MOVE_PMD
  mm: Speedup mremap on 1GB or larger regions
  arm64: Add set_pud_at() functions
  arm64: mremap speedup - Enable HAVE_MOVE_PUD
  x86: mremap speedup - Enable HAVE_MOVE_PUD

 arch/Kconfig                             |   7 +
 arch/arm64/Kconfig                       |   2 +
 arch/arm64/include/asm/pgtable.h         |   1 +
 arch/x86/Kconfig                         |   1 +
 mm/mremap.c                              | 220 +++++++++++++--
 tools/testing/selftests/vm/.gitignore    |   1 +
 tools/testing/selftests/vm/Makefile      |   1 +
 tools/testing/selftests/vm/mremap_test.c | 333 +++++++++++++++++++++++
 tools/testing/selftests/vm/run_vmtests   |  11 +
 9 files changed, 547 insertions(+), 30 deletions(-)
 create mode 100644 tools/testing/selftests/vm/mremap_test.c


base-commit: 472e5b056f000a778abb41f1e443de58eb259783
-- 
2.28.0.806.g8561365e88-goog

[PATCH v2 1/6] kselftests: vm: Add mremap tests

[Kalesh Singh]

Test mremap on regions of various sizes and alignments and validate
data after remapping. Also provide total time for remapping
the region which is useful for performance comparison of the mremap
optimizations that move pages at the PMD/PUD levels if HAVE_MOVE_PMD
and/or HAVE_MOVE_PUD are enabled.

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
Changes in v2:
  - Reduce test time by only validating a certain threshold of the
    remapped region (4MB by default). The -t flag can be used to
    set a custom threshold in MB or no threshold by passing 0. (-t0).
    mremap time is not provided in stdout for only partially validated
    regions. This time is only applicable for comparison if the entire
    mapped region was faulted in.
  - Use a random pattern for validating the remapped region. The -p
    flag can be used to run the tests with a specified seed for the
    random pattern.
  - Print test configs (threshold_mb and pattern_seed) to stdout.
  - Remove MAKE_SIMPLE_TEST macro.
  - Define named flags instead of 0 / 1.
  - Add comments for destination address' align_mask and offset.

 tools/testing/selftests/vm/.gitignore    |   1 +
 tools/testing/selftests/vm/Makefile      |   1 +
 tools/testing/selftests/vm/mremap_test.c | 333 +++++++++++++++++++++++
 tools/testing/selftests/vm/run_vmtests   |  11 +
 4 files changed, 346 insertions(+)
 create mode 100644 tools/testing/selftests/vm/mremap_test.c

diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore
index 849e8226395a..b3a183c36cb5 100644
--- a/tools/testing/selftests/vm/.gitignore
+++ b/tools/testing/selftests/vm/.gitignore
@@ -8,6 +8,7 @@ thuge-gen
 compaction_test
 mlock2-tests
 mremap_dontunmap
+mremap_test
 on-fault-limit
 transhuge-stress
 protection_keys
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index a9026706d597..f044808b45fa 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -16,6 +16,7 @@ TEST_GEN_FILES += map_populate
 TEST_GEN_FILES += mlock-random-test
 TEST_GEN_FILES += mlock2-tests
 TEST_GEN_FILES += mremap_dontunmap
+TEST_GEN_FILES += mremap_test
 TEST_GEN_FILES += on-fault-limit
 TEST_GEN_FILES += thuge-gen
 TEST_GEN_FILES += transhuge-stress
diff --git a/tools/testing/selftests/vm/mremap_test.c b/tools/testing/selftests/vm/mremap_test.c
new file mode 100644
index 000000000000..abe1f0a5a26a
--- /dev/null
+++ b/tools/testing/selftests/vm/mremap_test.c
@@ -0,0 +1,333 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2020 Google LLC
+ */
+#define _GNU_SOURCE
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <time.h>
+
+#include "../kselftest.h"
+
+#define EXPECT_SUCCESS 0
+#define EXPECT_FAILURE 1
+#define NON_OVERLAPPING 0
+#define OVERLAPPING 1
+#define NS_PER_SEC 1000000000ULL
+#define VALIDATION_DEFAULT_THRESHOLD 4	/* 4MB */
+#define VALIDATION_NO_THRESHOLD 0	/* Verify the entire region */
+#define PATTERN_SIZE 3
+
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+#define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
+
+struct config {
+	unsigned long long src_alignment;
+	unsigned long long dest_alignment;
+	unsigned long long region_size;
+	int overlapping;
+};
+
+struct test {
+	const char *name;
+	struct config config;
+	int expect_failure;
+};
+
+enum {
+	_1KB = 1ULL << 10,	/* 1KB -> not page aligned */
+	_4KB = 4ULL << 10,
+	_8KB = 8ULL << 10,
+	_1MB = 1ULL << 20,
+	_2MB = 2ULL << 20,
+	_4MB = 4ULL << 20,
+	_1GB = 1ULL << 30,
+	_2GB = 2ULL << 30,
+	PTE = _4KB,
+	PMD = _2MB,
+	PUD = _1GB,
+};
+
+#define MAKE_TEST(source_align, destination_align, size,	\
+		  overlaps, should_fail, test_name)		\
+{								\
+	.name = test_name,					\
+	.config = {						\
+		.src_alignment = source_align,			\
+		.dest_alignment = destination_align,		\
+		.region_size = size,				\
+		.overlapping = overlaps,			\
+	},							\
+	.expect_failure = should_fail				\
+}
+
+/*
+ * Returns the start address of the mapping on success, else returns
+ * NULL on failure.
+ */
+static void *get_source_mapping(struct config c)
+{
+	unsigned long long addr = 0ULL;
+	void *src_addr = NULL;
+retry:
+	addr += c.src_alignment;
+	src_addr = mmap((void *) addr, c.region_size, PROT_READ | PROT_WRITE,
+			MAP_FIXED | MAP_ANONYMOUS | MAP_SHARED, -1, 0);
+	if (src_addr == MAP_FAILED) {
+		if (errno == EPERM)
+			goto retry;
+		goto error;
+	}
+	/*
+	 * Check that the address is aligned to the specified alignment. Addresses
+	 * which have alignments that are multiples of that specified are not considered
+	 * valid. For instance, 1GB address is 2MB-aligned, however it will not be
+	 * considered valid for a requested alignment of 2MB. This is done to
+	 * reduce coincidental alignment in the tests.
+	 */
+	if (((unsigned long long) src_addr & (c.src_alignment - 1)) ||
+			!((unsigned long long) src_addr & c.src_alignment))
+		goto retry;
+
+	if (!src_addr)
+		goto error;
+
+	return src_addr;
+error:
+	ksft_print_msg("Failed to map source region: %s\n",
+			strerror(errno));
+	return NULL;
+}
+
+/* Returns the time taken for the remap on success else returns -1. */
+static long long remap_region(struct config c, unsigned int threshold_mb,
+			      char pattern_seed)
+{
+	void *addr, *src_addr, *dest_addr;
+	unsigned long long i;
+	struct timespec t_start = {0, 0}, t_end = {0, 0};
+	long long  start_ns, end_ns, align_mask, ret, offset;
+	unsigned long long threshold;
+
+	if (threshold_mb == VALIDATION_NO_THRESHOLD)
+		threshold = c.region_size;
+	else
+		threshold = MIN(threshold_mb * _1MB, c.region_size);
+
+	src_addr = get_source_mapping(c);
+	if (!src_addr) {
+		ret = -1;
+		goto out;
+	}
+
+	/* Set byte pattern */
+	srand(pattern_seed);
+	for (i = 0; i < threshold; i++)
+		memset((char *) src_addr + i, (char) rand(), 1);
+
+	/* Mask to zero out lower bits of address for alignment */
+	align_mask = ~(c.dest_alignment - 1);
+	/* Offset of destination address from the end of the source region */
+	offset = (c.overlapping) ? -c.dest_alignment : c.dest_alignment;
+	addr = (void *) (((unsigned long long) src_addr + c.region_size + offset)
+			& align_mask);
+
+	/* See comment in get_source_mapping() */
+	if (!((unsigned long long) addr & c.dest_alignment))
+		addr = (void *) ((unsigned long long) addr | c.dest_alignment);
+
+	clock_gettime(CLOCK_MONOTONIC, &t_start);
+	dest_addr = mremap(src_addr, c.region_size, c.region_size,
+			MREMAP_MAYMOVE|MREMAP_FIXED, (char *) addr);
+	clock_gettime(CLOCK_MONOTONIC, &t_end);
+
+	if (dest_addr == MAP_FAILED) {
+		ksft_print_msg("mremap failed: %s\n", strerror(errno));
+		ret = -1;
+		goto clean_up_src;
+	}
+
+	/* Verify byte pattern after remapping */
+	srand(pattern_seed);
+	for (i = 0; i < threshold; i++) {
+		char c = (char) rand();
+
+		if (((char *) dest_addr)[i] != c) {
+			ksft_print_msg("Data after remap doesn't match at offset %d\n",
+					i);
+			ksft_print_msg("Expected: %#x\t Got: %#x\n", c & 0xff,
+					((char *) dest_addr)[i] & 0xff);
+			ret = -1;
+			goto clean_up_dest;
+		}
+	}
+
+	start_ns = t_start.tv_sec * NS_PER_SEC + t_start.tv_nsec;
+	end_ns = t_end.tv_sec * NS_PER_SEC + t_end.tv_nsec;
+	ret = end_ns - start_ns;
+
+/*
+ * Since the destination address is specified using MREMAP_FIXED, subsequent mremap will unmap any
+ * previous mapping at the address range specified by dest_addr and region_size. This significantly
+ * affects the remap time of subsequent tests. So we clean up mappings after each test.
+ */
+clean_up_dest:
+	munmap(dest_addr, c.region_size);
+clean_up_src:
+	munmap(src_addr, c.region_size);
+out:
+	return ret;
+}
+
+static void run_mremap_test_case(struct test test_case, int *failures, unsigned int threshold_mb,
+				 unsigned int pattern_seed)
+{
+	long long remap_time = remap_region(test_case.config, threshold_mb, pattern_seed);
+
+	if (remap_time < 0) {
+		if (test_case.expect_failure)
+			ksft_test_result_pass("%s\n\tExpected mremap failure\n", test_case.name);
+		else {
+			ksft_test_result_fail("%s\n", test_case.name);
+			*failures += 1;
+		}
+	} else {
+		/* Comparing mremap time is only applicable if entire region was faulted in */
+		if (threshold_mb == VALIDATION_NO_THRESHOLD ||
+		    test_case.config.region_size <= threshold_mb * _1MB)
+			ksft_test_result_pass("%s\n\tmremap time: %12lldns\n",
+					      test_case.name, remap_time);
+		else
+			ksft_test_result_pass("%s\n", test_case.name);
+	}
+}
+
+static void usage(const char *cmd)
+{
+	fprintf(stderr,
+		"Usage: %s [[-t <threshold_mb>] [-p <pattern_seed>]]\n"
+		"-t\t only validate threshold_mb of the remapped region\n"
+		"  \t if 0 is supplied no threshold is used; all tests\n"
+		"  \t are run and remapped regions validated fully.\n"
+		"  \t The default threshold used is 4MB.\n"
+		"-p\t provide a seed to generate the random pattern for\n"
+		"  \t validating the remapped region.\n", cmd);
+}
+
+static int parse_args(int argc, char **argv, unsigned int *threshold_mb,
+		      unsigned int *pattern_seed)
+{
+	const char *optstr = "t:p:";
+	int opt;
+
+	while ((opt = getopt(argc, argv, optstr)) != -1) {
+		switch (opt) {
+		case 't':
+			*threshold_mb = atoi(optarg);
+			break;
+		case 'p':
+			*pattern_seed = atoi(optarg);
+			break;
+		default:
+			usage(argv[0]);
+			return -1;
+		}
+	}
+
+	if (optind < argc) {
+		usage(argv[0]);
+		return -1;
+	}
+
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	int failures = 0;
+	int i, run_perf_tests;
+	unsigned int threshold_mb = VALIDATION_DEFAULT_THRESHOLD;
+	unsigned int pattern_seed;
+	time_t t;
+
+	pattern_seed = (unsigned int) time(&t);
+
+	if (parse_args(argc, argv, &threshold_mb, &pattern_seed) < 0)
+		exit(EXIT_FAILURE);
+
+	ksft_print_msg("Test configs:\n\tthreshold_mb=%u\n\tpattern_seed=%u\n\n",
+		       threshold_mb, pattern_seed);
+
+	struct test test_cases[] = {
+		/* Expected mremap failures */
+		MAKE_TEST(_4KB, _4KB, _4KB, OVERLAPPING, EXPECT_FAILURE,
+			  "mremap - Source and Destination Regions Overlapping"),
+		MAKE_TEST(_4KB, _1KB, _4KB, NON_OVERLAPPING, EXPECT_FAILURE,
+			  "mremap - Destination Address Misaligned (1KB-aligned)"),
+		MAKE_TEST(_1KB, _4KB, _4KB, NON_OVERLAPPING, EXPECT_FAILURE,
+			  "mremap - Source Address Misaligned (1KB-aligned)"),
+
+		/* Src addr PTE aligned */
+		MAKE_TEST(PTE, PTE, _8KB, NON_OVERLAPPING, EXPECT_SUCCESS,
+			  "8KB mremap - Source PTE-aligned, Destination PTE-aligned"),
+
+		/* Src addr 1MB aligned */
+		MAKE_TEST(_1MB, PTE, _2MB, NON_OVERLAPPING, EXPECT_SUCCESS,
+			  "2MB mremap - Source 1MB-aligned, Destination PTE-aligned"),
+		MAKE_TEST(_1MB, _1MB, _2MB, NON_OVERLAPPING, EXPECT_SUCCESS,
+			  "2MB mremap - Source 1MB-aligned, Destination 1MB-aligned"),
+
+		/* Src addr PMD aligned */
+		MAKE_TEST(PMD, PTE, _4MB, NON_OVERLAPPING, EXPECT_SUCCESS,
+			  "4MB mremap - Source PMD-aligned, Destination PTE-aligned"),
+		MAKE_TEST(PMD, _1MB, _4MB, NON_OVERLAPPING, EXPECT_SUCCESS,
+			  "4MB mremap - Source PMD-aligned, Destination 1MB-aligned"),
+		MAKE_TEST(PMD, PMD, _4MB, NON_OVERLAPPING, EXPECT_SUCCESS,
+			  "4MB mremap - Source PMD-aligned, Destination PMD-aligned"),
+
+		/* Src addr PUD aligned */
+		MAKE_TEST(PUD, PTE, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
+			  "2GB mremap - Source PUD-aligned, Destination PTE-aligned"),
+		MAKE_TEST(PUD, _1MB, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
+			  "2GB mremap - Source PUD-aligned, Destination 1MB-aligned"),
+		MAKE_TEST(PUD, PMD, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
+			  "2GB mremap - Source PUD-aligned, Destination PMD-aligned"),
+		MAKE_TEST(PUD, PUD, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
+			  "2GB mremap - Source PUD-aligned, Destination PUD-aligned"),
+	};
+
+	struct test perf_test_cases[] = {
+		/* mremap 1GB region - Page table level aligned time comparison */
+		MAKE_TEST(PTE, PTE, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS,
+			  "1GB mremap - Source PTE-aligned, Destination PTE-aligned"),
+		MAKE_TEST(PMD, PMD, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS,
+			  "1GB mremap - Source PMD-aligned, Destination PMD-aligned"),
+		MAKE_TEST(PUD, PUD, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS,
+			  "1GB mremap - Source PUD-aligned, Destination PUD-aligned"),
+	};
+
+	run_perf_tests =  (threshold_mb == VALIDATION_NO_THRESHOLD) ||
+				(threshold_mb * _1MB >= _1GB);
+
+	ksft_set_plan(ARRAY_SIZE(test_cases) + (run_perf_tests ?
+		      ARRAY_SIZE(perf_test_cases) : 0));
+
+	for (i = 0; i < ARRAY_SIZE(test_cases); i++)
+		run_mremap_test_case(test_cases[i], &failures, threshold_mb, pattern_seed);
+
+	if (run_perf_tests) {
+		ksft_print_msg("\n%s\n",
+		 "mremap HAVE_MOVE_PMD/PUD optimization time comparison for 1GB region:");
+		for (i = 0; i < ARRAY_SIZE(perf_test_cases); i++)
+			run_mremap_test_case(perf_test_cases[i], &failures, threshold_mb,
+					     pattern_seed);
+	}
+
+	if (failures > 0)
+		ksft_exit_fail();
+	else
+		ksft_exit_pass();
+}
diff --git a/tools/testing/selftests/vm/run_vmtests b/tools/testing/selftests/vm/run_vmtests
index a3f4f30f0a2e..d578ad831813 100755
--- a/tools/testing/selftests/vm/run_vmtests
+++ b/tools/testing/selftests/vm/run_vmtests
@@ -241,6 +241,17 @@ else
 	echo "[PASS]"
 fi
 
+echo "-------------------"
+echo "running mremap_test"
+echo "-------------------"
+./mremap_test
+if [ $? -ne 0 ]; then
+	echo "[FAIL]"
+	exitcode=1
+else
+	echo "[PASS]"
+fi
+
 echo "-----------------"
 echo "running thuge-gen"
 echo "-----------------"
-- 
2.28.0.806.g8561365e88-goog

[PATCH v2 2/6] arm64: mremap speedup - Enable HAVE_MOVE_PMD

[Kalesh Singh]

HAVE_MOVE_PMD enables remapping pages at the PMD level if both the
source and destination addresses are PMD-aligned.

HAVE_MOVE_PMD is already enabled on x86. The original patch [1] that
introduced this config did not enable it on arm64 at the time because
of performance issues with flushing the TLB on every PMD move. These
issues have since been addressed in more recent releases with
improvements to the arm64 TLB invalidation and core mmu_gather code as
Will Deacon mentioned in [2].

From the data below, it can be inferred that there is approximately
8x improvement in performance when HAVE_MOVE_PMD is enabled on arm64.

--------- Test Results ----------

The following results were obtained on an arm64 device running a 5.4
kernel, by remapping a PMD-aligned, 1GB sized region to a PMD-aligned
destination. The results from 10 iterations of the test are given below.
All times are in nanoseconds.

Control    HAVE_MOVE_PMD

9220833    1247761
9002552    1219896
9254115    1094792
8725885    1227760
9308646    1043698
9001667    1101771
8793385    1159896
8774636    1143594
9553125    1025833
9374010    1078125

9100885.4  1134312.6    <-- Mean Time in nanoseconds

Total mremap time for a 1GB sized PMD-aligned region drops from
~9.1 milliseconds to ~1.1 milliseconds. (~8x speedup).

[1] https://lore.kernel.org/r/20181108181201.88826-3-joelaf@google.com
[2] https://www.mail-archive.com/linuxppc-dev@lists.ozlabs.org/msg140837.html

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
 arch/arm64/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 6d232837cbee..844d089668e3 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -121,6 +121,7 @@ config ARM64
 	select GENERIC_VDSO_TIME_NS
 	select HANDLE_DOMAIN_IRQ
 	select HARDIRQS_SW_RESEND
+	select HAVE_MOVE_PMD
 	select HAVE_PCI
 	select HAVE_ACPI_APEI if (ACPI && EFI)
 	select HAVE_ALIGNED_STRUCT_PAGE if SLUB
-- 
2.28.0.806.g8561365e88-goog

[PATCH v2 3/6] mm: Speedup mremap on 1GB or larger regions

[Kalesh Singh]

Android needs to move large memory regions for garbage collection.
The GC requires moving physical pages of multi-gigabyte heap
using mremap. During this move, the application threads have to
be paused for correctness. It is critical to keep this pause as
short as possible to avoid jitters during user interaction.

Optimize mremap for >= 1GB-sized regions by moving at the PUD/PGD
level if the source and destination addresses are PUD-aligned.
For CONFIG_PGTABLE_LEVELS == 3, moving at the PUD level in effect moves
PGD entries, since the PUD entry is “folded back” onto the PGD entry.
Add HAVE_MOVE_PUD so that architectures where moving at the PUD level
isn't supported/tested can turn this off by not selecting the config.

Fix build test error from v1 of this series reported by
kernel test robot in [1].

[1] https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org/thread/CKPGL4FH4NG7TGH2CVYX2UX76L25BTA3/

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Reported-by: kernel test robot <lkp@intel.com>
---
Changes in v2:
  - Update commit message with description of Android GC's use case.
  - Move set_pud_at() to a separate patch.
  - Use switch() instead of ifs in move_pgt_entry()
  - Fix build test error reported by kernel test robot on x86_64 in [1].
    Guard move_huge_pmd() with IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE),
    since this section doesn't get optimized out in the kernel test
    robot's build test when HAVE_MOVE_PUD is enabled.
  - Keep WARN_ON_ONCE(1) instead of BUILD_BUG() for the aforementioned
    reason.

 arch/Kconfig |   7 ++
 mm/mremap.c  | 220 ++++++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 197 insertions(+), 30 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index af14a567b493..5eabaa00bf9b 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -602,6 +602,13 @@ config HAVE_IRQ_TIME_ACCOUNTING
 	  Archs need to ensure they use a high enough resolution clock to
 	  support irq time accounting and then call enable_sched_clock_irqtime().
 
+config HAVE_MOVE_PUD
+	bool
+	help
+	  Architectures that select this are able to move page tables at the
+	  PUD level. If there are only 3 page table levels, the move effectively
+	  happens at the PGD level.
+
 config HAVE_MOVE_PMD
 	bool
 	help
diff --git a/mm/mremap.c b/mm/mremap.c
index 138abbae4f75..c1d6ab667d70 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -249,14 +249,176 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
 
 	return true;
 }
+#else
+static inline bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
+		  unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
+{
+	return false;
+}
 #endif
 
+#ifdef CONFIG_HAVE_MOVE_PUD
+static pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr)
+{
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+
+	pgd = pgd_offset(mm, addr);
+	if (pgd_none_or_clear_bad(pgd))
+		return NULL;
+
+	p4d = p4d_offset(pgd, addr);
+	if (p4d_none_or_clear_bad(p4d))
+		return NULL;
+
+	pud = pud_offset(p4d, addr);
+	if (pud_none_or_clear_bad(pud))
+		return NULL;
+
+	return pud;
+}
+
+static pud_t *alloc_new_pud(struct mm_struct *mm, struct vm_area_struct *vma,
+			    unsigned long addr)
+{
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+
+	pgd = pgd_offset(mm, addr);
+	p4d = p4d_alloc(mm, pgd, addr);
+	if (!p4d)
+		return NULL;
+	pud = pud_alloc(mm, p4d, addr);
+	if (!pud)
+		return NULL;
+
+	return pud;
+}
+
+static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
+		  unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
+{
+	spinlock_t *old_ptl, *new_ptl;
+	struct mm_struct *mm = vma->vm_mm;
+	pud_t pud;
+
+	/*
+	 * The destination pud shouldn't be established, free_pgtables()
+	 * should have released it.
+	 */
+	if (WARN_ON_ONCE(!pud_none(*new_pud)))
+		return false;
+
+	/*
+	 * We don't have to worry about the ordering of src and dst
+	 * ptlocks because exclusive mmap_lock prevents deadlock.
+	 */
+	old_ptl = pud_lock(vma->vm_mm, old_pud);
+	new_ptl = pud_lockptr(mm, new_pud);
+	if (new_ptl != old_ptl)
+		spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
+
+	/* Clear the pud */
+	pud = *old_pud;
+	pud_clear(old_pud);
+
+	VM_BUG_ON(!pud_none(*new_pud));
+
+	/* Set the new pud */
+	set_pud_at(mm, new_addr, new_pud, pud);
+	flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE);
+	if (new_ptl != old_ptl)
+		spin_unlock(new_ptl);
+	spin_unlock(old_ptl);
+
+	return true;
+}
+#else
+static inline bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
+		  unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
+{
+	return false;
+}
+#endif
+
+enum pgt_entry {
+	NORMAL_PMD,
+	HPAGE_PMD,
+	NORMAL_PUD,
+};
+
+/*
+ * Returns an extent of the corresponding size for the pgt_entry specified if valid.
+ * Else returns a smaller extent bounded by the end of the source and destination
+ * pgt_entry. Returns 0 if an invalid pgt_entry is specified.
+ */
+static unsigned long get_extent(enum pgt_entry entry, unsigned long old_addr,
+			unsigned long old_end, unsigned long new_addr)
+{
+	unsigned long next, extent, mask, size;
+
+	if (entry == NORMAL_PMD || entry == HPAGE_PMD) {
+		mask = PMD_MASK;
+		size = PMD_SIZE;
+	} else if (entry == NORMAL_PUD) {
+		mask = PUD_MASK;
+		size = PUD_SIZE;
+	} else
+		return 0;
+
+	next = (old_addr + size) & mask;
+	/* even if next overflowed, extent below will be ok */
+	extent = (next > old_end) ? old_end - old_addr : next - old_addr;
+	next = (new_addr + size) & mask;
+	if (extent > next - new_addr)
+		extent = next - new_addr;
+	return extent;
+}
+
+/*
+ * Attempts to speedup the move by moving entry at the level corresponding to
+ * pgt_entry. Returns true if the move was successful, else false.
+ */
+static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma,
+			unsigned long old_addr, unsigned long new_addr, void *old_entry,
+			void *new_entry, bool need_rmap_locks)
+{
+	bool moved = false;
+
+	/* See comment in move_ptes() */
+	if (need_rmap_locks)
+		take_rmap_locks(vma);
+
+	switch (entry) {
+	case NORMAL_PMD:
+		moved =  move_normal_pmd(vma, old_addr, new_addr, old_entry, new_entry);
+		break;
+	case NORMAL_PUD:
+		moved =  move_normal_pud(vma, old_addr, new_addr, old_entry, new_entry);
+		break;
+	case HPAGE_PMD:
+		moved =  IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+			move_huge_pmd(vma, old_addr, new_addr, old_entry, new_entry);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+
+	if (need_rmap_locks)
+		drop_rmap_locks(vma);
+
+	return moved;
+}
+
 unsigned long move_page_tables(struct vm_area_struct *vma,
 		unsigned long old_addr, struct vm_area_struct *new_vma,
 		unsigned long new_addr, unsigned long len,
 		bool need_rmap_locks)
 {
-	unsigned long extent, next, old_end;
+	unsigned long extent, old_end;
 	struct mmu_notifier_range range;
 	pmd_t *old_pmd, *new_pmd;
 
@@ -269,14 +431,27 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
 
 	for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 		cond_resched();
-		next = (old_addr + PMD_SIZE) & PMD_MASK;
-		/* even if next overflowed, extent below will be ok */
-		extent = next - old_addr;
-		if (extent > old_end - old_addr)
-			extent = old_end - old_addr;
-		next = (new_addr + PMD_SIZE) & PMD_MASK;
-		if (extent > next - new_addr)
-			extent = next - new_addr;
+#ifdef CONFIG_HAVE_MOVE_PUD
+		/*
+		 * If extent is PUD-sized try to speed up the move by moving at the
+		 * PUD level if possible.
+		 */
+		extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr);
+		if (extent == PUD_SIZE) {
+			pud_t *old_pud, *new_pud;
+
+			old_pud = get_old_pud(vma->vm_mm, old_addr);
+			if (!old_pud)
+				continue;
+			new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr);
+			if (!new_pud)
+				break;
+			if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr,
+					   old_pud, new_pud, need_rmap_locks))
+				continue;
+		}
+#endif
+		extent = get_extent(NORMAL_PMD, old_addr, old_end, new_addr);
 		old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 		if (!old_pmd)
 			continue;
@@ -284,18 +459,10 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
 		if (!new_pmd)
 			break;
 		if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) || pmd_devmap(*old_pmd)) {
-			if (extent == HPAGE_PMD_SIZE) {
-				bool moved;
-				/* See comment in move_ptes() */
-				if (need_rmap_locks)
-					take_rmap_locks(vma);
-				moved = move_huge_pmd(vma, old_addr, new_addr,
-						      old_pmd, new_pmd);
-				if (need_rmap_locks)
-					drop_rmap_locks(vma);
-				if (moved)
-					continue;
-			}
+			if (extent == HPAGE_PMD_SIZE &&
+			    move_pgt_entry(HPAGE_PMD, vma, old_addr, new_addr, old_pmd,
+					   new_pmd, need_rmap_locks))
+				continue;
 			split_huge_pmd(vma, old_pmd, old_addr);
 			if (pmd_trans_unstable(old_pmd))
 				continue;
@@ -305,15 +472,8 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
 			 * If the extent is PMD-sized, try to speed the move by
 			 * moving at the PMD level if possible.
 			 */
-			bool moved;
-
-			if (need_rmap_locks)
-				take_rmap_locks(vma);
-			moved = move_normal_pmd(vma, old_addr, new_addr,
-						old_pmd, new_pmd);
-			if (need_rmap_locks)
-				drop_rmap_locks(vma);
-			if (moved)
+			if (move_pgt_entry(NORMAL_PMD, vma, old_addr, new_addr, old_pmd,
+					   new_pmd, need_rmap_locks))
 				continue;
 #endif
 		}
-- 
2.28.0.806.g8561365e88-goog

[PATCH v2 4/6] arm64: Add set_pud_at() function

[Kalesh Singh]

set_pud_at() is used in move_normal_pud() for remapping
pages at the PUD level.

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
 arch/arm64/include/asm/pgtable.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index d5d3fbe73953..8848125e3024 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -415,6 +415,7 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
 #define pfn_pud(pfn,prot)	__pud(__phys_to_pud_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
 
 #define set_pmd_at(mm, addr, pmdp, pmd)	set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd))
+#define set_pud_at(mm, addr, pudp, pud)	set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud))
 
 #define __p4d_to_phys(p4d)	__pte_to_phys(p4d_pte(p4d))
 #define __phys_to_p4d_val(phys)	__phys_to_pte_val(phys)
-- 
2.28.0.806.g8561365e88-goog

[PATCH v2 5/6] arm64: mremap speedup - Enable HAVE_MOVE_PUD

[Kalesh Singh]

HAVE_MOVE_PUD enables remapping pages at the PUD level if both the
source and destination addresses are PUD-aligned.

With HAVE_MOVE_PUD enabled it can be inferred that there is approximately
a 19x improvement in performance on arm64. (See data below).

------- Test Results ---------

The following results were obtained using a 5.4 kernel, by remapping
a PUD-aligned, 1GB sized region to a PUD-aligned destination.
The results from 10 iterations of the test are given below:

Total mremap times for 1GB data on arm64. All times are in nanoseconds.

Control          HAVE_MOVE_PUD

1247761          74271
1219896          46771
1094792          59687
1227760          48385
1043698          76666
1101771          50365
1159896          52500
1143594          75261
1025833          61354
1078125          48697

1134312.6        59395.7    <-- Mean time in nanoseconds

A 1GB mremap completion time drops from ~1.1 milliseconds
to ~59 microseconds on arm64. (~19x speed up).

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
 arch/arm64/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 844d089668e3..4d521f0a5863 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -122,6 +122,7 @@ config ARM64
 	select HANDLE_DOMAIN_IRQ
 	select HARDIRQS_SW_RESEND
 	select HAVE_MOVE_PMD
+	select HAVE_MOVE_PUD
 	select HAVE_PCI
 	select HAVE_ACPI_APEI if (ACPI && EFI)
 	select HAVE_ALIGNED_STRUCT_PAGE if SLUB
-- 
2.28.0.806.g8561365e88-goog

[PATCH v2 6/6] x86: mremap speedup - Enable HAVE_MOVE_PUD

[Kalesh Singh]

HAVE_MOVE_PUD enables remapping pages at the PUD level if both the
source and destination addresses are PUD-aligned.

With HAVE_MOVE_PUD enabled it can be inferred that there is approximately
a 13x improvement in performance on x86. (See data below).

------- Test Results ---------

The following results were obtained using a 5.4 kernel, by remapping
a PUD-aligned, 1GB sized region to a PUD-aligned destination.
The results from 10 iterations of the test are given below:

Total mremap times for 1GB data on x86. All times are in nanoseconds.

Control        HAVE_MOVE_PUD

180394         15089
235728         14056
238931         25741
187330         13838
241742         14187
177925         14778
182758         14728
160872         14418
205813         15107
245722         13998

205721.5       15594    <-- Mean time in nanoseconds

A 1GB mremap completion time drops from ~205 microseconds
to ~15 microseconds on x86. (~13x speed up).

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
 arch/x86/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7101ac64bb20..ff6e2755cab8 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -198,6 +198,7 @@ config X86
 	select HAVE_MIXED_BREAKPOINTS_REGS
 	select HAVE_MOD_ARCH_SPECIFIC
 	select HAVE_MOVE_PMD
+	select HAVE_MOVE_PUD
 	select HAVE_NMI
 	select HAVE_OPROFILE
 	select HAVE_OPTPROBES
-- 
2.28.0.806.g8561365e88-goog

Re: [PATCH v2 3/6] mm: Speedup mremap on 1GB or larger regions

[Kirill A. Shutemov]

On Fri, Oct 02, 2020 at 04:20:48PM +0000, Kalesh Singh wrote:
> Android needs to move large memory regions for garbage collection.
> The GC requires moving physical pages of multi-gigabyte heap
> using mremap. During this move, the application threads have to
> be paused for correctness. It is critical to keep this pause as
> short as possible to avoid jitters during user interaction.
> 
> Optimize mremap for >= 1GB-sized regions by moving at the PUD/PGD
> level if the source and destination addresses are PUD-aligned.
> For CONFIG_PGTABLE_LEVELS == 3, moving at the PUD level in effect moves
> PGD entries, since the PUD entry is “folded back” onto the PGD entry.
> Add HAVE_MOVE_PUD so that architectures where moving at the PUD level
> isn't supported/tested can turn this off by not selecting the config.
> 
> Fix build test error from v1 of this series reported by
> kernel test robot in [1].
> 
> [1] https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org/thread/CKPGL4FH4NG7TGH2CVYX2UX76L25BTA3/
> 
> Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
> Reported-by: kernel test robot <lkp@intel.com>
> ---
> Changes in v2:
>   - Update commit message with description of Android GC's use case.
>   - Move set_pud_at() to a separate patch.
>   - Use switch() instead of ifs in move_pgt_entry()
>   - Fix build test error reported by kernel test robot on x86_64 in [1].
>     Guard move_huge_pmd() with IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE),
>     since this section doesn't get optimized out in the kernel test
>     robot's build test when HAVE_MOVE_PUD is enabled.
>   - Keep WARN_ON_ONCE(1) instead of BUILD_BUG() for the aforementioned
>     reason.

Okay, but IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) on the caller side would
do the trick, I believe.

> 
>  arch/Kconfig |   7 ++
>  mm/mremap.c  | 220 ++++++++++++++++++++++++++++++++++++++++++++-------
>  2 files changed, 197 insertions(+), 30 deletions(-)
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index af14a567b493..5eabaa00bf9b 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -602,6 +602,13 @@ config HAVE_IRQ_TIME_ACCOUNTING
>  	  Archs need to ensure they use a high enough resolution clock to
>  	  support irq time accounting and then call enable_sched_clock_irqtime().
>  
> +config HAVE_MOVE_PUD
> +	bool
> +	help
> +	  Architectures that select this are able to move page tables at the
> +	  PUD level. If there are only 3 page table levels, the move effectively
> +	  happens at the PGD level.
> +
>  config HAVE_MOVE_PMD
>  	bool
>  	help
> diff --git a/mm/mremap.c b/mm/mremap.c
> index 138abbae4f75..c1d6ab667d70 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -249,14 +249,176 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
>  
>  	return true;
>  }
> +#else
> +static inline bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
> +		  unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
> +{
> +	return false;
> +}
>  #endif
>  
> +#ifdef CONFIG_HAVE_MOVE_PUD
> +static pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr)
> +{
> +	pgd_t *pgd;
> +	p4d_t *p4d;
> +	pud_t *pud;
> +
> +	pgd = pgd_offset(mm, addr);
> +	if (pgd_none_or_clear_bad(pgd))
> +		return NULL;
> +
> +	p4d = p4d_offset(pgd, addr);
> +	if (p4d_none_or_clear_bad(p4d))
> +		return NULL;
> +
> +	pud = pud_offset(p4d, addr);
> +	if (pud_none_or_clear_bad(pud))
> +		return NULL;
> +
> +	return pud;
> +}
> +
> +static pud_t *alloc_new_pud(struct mm_struct *mm, struct vm_area_struct *vma,
> +			    unsigned long addr)
> +{
> +	pgd_t *pgd;
> +	p4d_t *p4d;
> +	pud_t *pud;
> +
> +	pgd = pgd_offset(mm, addr);
> +	p4d = p4d_alloc(mm, pgd, addr);
> +	if (!p4d)
> +		return NULL;
> +	pud = pud_alloc(mm, p4d, addr);
> +	if (!pud)
> +		return NULL;
> +
> +	return pud;
> +}

Looks like a code duplication.

Could you move these two helpers out of #ifdef CONFIG_HAVE_MOVE_PUD and
make get_old_pmd() and alloc_new_pmd() use them?

> +
> +static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
> +		  unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
> +{
> +	spinlock_t *old_ptl, *new_ptl;
> +	struct mm_struct *mm = vma->vm_mm;
> +	pud_t pud;
> +
> +	/*
> +	 * The destination pud shouldn't be established, free_pgtables()
> +	 * should have released it.
> +	 */
> +	if (WARN_ON_ONCE(!pud_none(*new_pud)))
> +		return false;
> +
> +	/*
> +	 * We don't have to worry about the ordering of src and dst
> +	 * ptlocks because exclusive mmap_lock prevents deadlock.
> +	 */
> +	old_ptl = pud_lock(vma->vm_mm, old_pud);
> +	new_ptl = pud_lockptr(mm, new_pud);
> +	if (new_ptl != old_ptl)
> +		spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
> +
> +	/* Clear the pud */
> +	pud = *old_pud;
> +	pud_clear(old_pud);
> +
> +	VM_BUG_ON(!pud_none(*new_pud));
> +
> +	/* Set the new pud */
> +	set_pud_at(mm, new_addr, new_pud, pud);
> +	flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE);
> +	if (new_ptl != old_ptl)
> +		spin_unlock(new_ptl);
> +	spin_unlock(old_ptl);
> +
> +	return true;
> +}
> +#else
> +static inline bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
> +		  unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
> +{
> +	return false;
> +}
> +#endif
> +
> +enum pgt_entry {
> +	NORMAL_PMD,
> +	HPAGE_PMD,
> +	NORMAL_PUD,
> +};
> +
> +/*
> + * Returns an extent of the corresponding size for the pgt_entry specified if valid.
> + * Else returns a smaller extent bounded by the end of the source and destination
> + * pgt_entry. Returns 0 if an invalid pgt_entry is specified.
> + */
> +static unsigned long get_extent(enum pgt_entry entry, unsigned long old_addr,
> +			unsigned long old_end, unsigned long new_addr)
> +{
> +	unsigned long next, extent, mask, size;
> +
> +	if (entry == NORMAL_PMD || entry == HPAGE_PMD) {
> +		mask = PMD_MASK;
> +		size = PMD_SIZE;
> +	} else if (entry == NORMAL_PUD) {
> +		mask = PUD_MASK;
> +		size = PUD_SIZE;
> +	} else
> +		return 0;

Em. Who would ever specify invalid pgt_entry? It's bug.
Again, switch()?

> +
> +	next = (old_addr + size) & mask;
> +	/* even if next overflowed, extent below will be ok */
> +	extent = (next > old_end) ? old_end - old_addr : next - old_addr;
> +	next = (new_addr + size) & mask;
> +	if (extent > next - new_addr)
> +		extent = next - new_addr;
> +	return extent;
> +}
> +
> +/*
> + * Attempts to speedup the move by moving entry at the level corresponding to
> + * pgt_entry. Returns true if the move was successful, else false.
> + */
> +static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma,
> +			unsigned long old_addr, unsigned long new_addr, void *old_entry,
> +			void *new_entry, bool need_rmap_locks)
> +{
> +	bool moved = false;
> +
> +	/* See comment in move_ptes() */
> +	if (need_rmap_locks)
> +		take_rmap_locks(vma);
> +
> +	switch (entry) {
> +	case NORMAL_PMD:
> +		moved =  move_normal_pmd(vma, old_addr, new_addr, old_entry, new_entry);

Nit: here and below, double space after '='. Why?

> +		break;
> +	case NORMAL_PUD:
> +		moved =  move_normal_pud(vma, old_addr, new_addr, old_entry, new_entry);
> +		break;
> +	case HPAGE_PMD:
> +		moved =  IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
> +			move_huge_pmd(vma, old_addr, new_addr, old_entry, new_entry);
> +		break;
> +	default:
> +		WARN_ON_ONCE(1);
> +		break;
> +	}
> +
> +	if (need_rmap_locks)
> +		drop_rmap_locks(vma);
> +
> +	return moved;
> +}
> +
>  unsigned long move_page_tables(struct vm_area_struct *vma,
>  		unsigned long old_addr, struct vm_area_struct *new_vma,
>  		unsigned long new_addr, unsigned long len,
>  		bool need_rmap_locks)
>  {
> -	unsigned long extent, next, old_end;
> +	unsigned long extent, old_end;
>  	struct mmu_notifier_range range;
>  	pmd_t *old_pmd, *new_pmd;
>  
> @@ -269,14 +431,27 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
>  
>  	for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
>  		cond_resched();
> -		next = (old_addr + PMD_SIZE) & PMD_MASK;
> -		/* even if next overflowed, extent below will be ok */
> -		extent = next - old_addr;
> -		if (extent > old_end - old_addr)
> -			extent = old_end - old_addr;
> -		next = (new_addr + PMD_SIZE) & PMD_MASK;
> -		if (extent > next - new_addr)
> -			extent = next - new_addr;
> +#ifdef CONFIG_HAVE_MOVE_PUD

Any chance  if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD)) would work here?

> +		/*
> +		 * If extent is PUD-sized try to speed up the move by moving at the
> +		 * PUD level if possible.
> +		 */
> +		extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr);
> +		if (extent == PUD_SIZE) {
> +			pud_t *old_pud, *new_pud;
> +
> +			old_pud = get_old_pud(vma->vm_mm, old_addr);
> +			if (!old_pud)
> +				continue;
> +			new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr);
> +			if (!new_pud)
> +				break;
> +			if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr,
> +					   old_pud, new_pud, need_rmap_locks))
> +				continue;
> +		}
> +#endif
> +		extent = get_extent(NORMAL_PMD, old_addr, old_end, new_addr);
>  		old_pmd = get_old_pmd(vma->vm_mm, old_addr);
>  		if (!old_pmd)
>  			continue;
> @@ -284,18 +459,10 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
>  		if (!new_pmd)
>  			break;
>  		if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) || pmd_devmap(*old_pmd)) {
> -			if (extent == HPAGE_PMD_SIZE) {
> -				bool moved;
> -				/* See comment in move_ptes() */
> -				if (need_rmap_locks)
> -					take_rmap_locks(vma);
> -				moved = move_huge_pmd(vma, old_addr, new_addr,
> -						      old_pmd, new_pmd);
> -				if (need_rmap_locks)
> -					drop_rmap_locks(vma);
> -				if (moved)
> -					continue;
> -			}
> +			if (extent == HPAGE_PMD_SIZE &&
> +			    move_pgt_entry(HPAGE_PMD, vma, old_addr, new_addr, old_pmd,
> +					   new_pmd, need_rmap_locks))
> +				continue;
>  			split_huge_pmd(vma, old_pmd, old_addr);
>  			if (pmd_trans_unstable(old_pmd))
>  				continue;
> @@ -305,15 +472,8 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
>  			 * If the extent is PMD-sized, try to speed the move by
>  			 * moving at the PMD level if possible.
>  			 */
> -			bool moved;
> -
> -			if (need_rmap_locks)
> -				take_rmap_locks(vma);
> -			moved = move_normal_pmd(vma, old_addr, new_addr,
> -						old_pmd, new_pmd);
> -			if (need_rmap_locks)
> -				drop_rmap_locks(vma);
> -			if (moved)
> +			if (move_pgt_entry(NORMAL_PMD, vma, old_addr, new_addr, old_pmd,
> +					   new_pmd, need_rmap_locks))
>  				continue;
>  #endif
>  		}
> -- 
> 2.28.0.806.g8561365e88-goog
> 

-- 
 Kirill A. Shutemov

Re: [PATCH v2 4/6] arm64: Add set_pud_at() function

[Kirill A. Shutemov]

On Fri, Oct 02, 2020 at 04:20:49PM +0000, Kalesh Singh wrote:
> set_pud_at() is used in move_normal_pud() for remapping
> pages at the PUD level.
> 
> Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
> ---
>  arch/arm64/include/asm/pgtable.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index d5d3fbe73953..8848125e3024 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -415,6 +415,7 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
>  #define pfn_pud(pfn,prot)	__pud(__phys_to_pud_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
>  
>  #define set_pmd_at(mm, addr, pmdp, pmd)	set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd))
> +#define set_pud_at(mm, addr, pudp, pud)	set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud))
>  
>  #define __p4d_to_phys(p4d)	__pte_to_phys(p4d_pte(p4d))
>  #define __phys_to_p4d_val(phys)	__phys_to_pte_val(phys)

Just fold it into the next patch.

-- 
 Kirill A. Shutemov

Re: [PATCH v2 3/6] mm: Speedup mremap on 1GB or larger regions

[Kalesh Singh]

Hi Kirill, thank you for the feedback.

On Fri, Oct 2, 2020 at 12:51 PM Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> On Fri, Oct 02, 2020 at 04:20:48PM +0000, Kalesh Singh wrote:
> > Android needs to move large memory regions for garbage collection.
> > The GC requires moving physical pages of multi-gigabyte heap
> > using mremap. During this move, the application threads have to
> > be paused for correctness. It is critical to keep this pause as
> > short as possible to avoid jitters during user interaction.
> >
> > Optimize mremap for >= 1GB-sized regions by moving at the PUD/PGD
> > level if the source and destination addresses are PUD-aligned.
> > For CONFIG_PGTABLE_LEVELS == 3, moving at the PUD level in effect moves
> > PGD entries, since the PUD entry is “folded back” onto the PGD entry.
> > Add HAVE_MOVE_PUD so that architectures where moving at the PUD level
> > isn't supported/tested can turn this off by not selecting the config.
> >
> > Fix build test error from v1 of this series reported by
> > kernel test robot in [1].
> >
> > [1] https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org/thread/CKPGL4FH4NG7TGH2CVYX2UX76L25BTA3/
> >
> > Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
> > Reported-by: kernel test robot <lkp@intel.com>
> > ---
> > Changes in v2:
> >   - Update commit message with description of Android GC's use case.
> >   - Move set_pud_at() to a separate patch.
> >   - Use switch() instead of ifs in move_pgt_entry()
> >   - Fix build test error reported by kernel test robot on x86_64 in [1].
> >     Guard move_huge_pmd() with IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE),
> >     since this section doesn't get optimized out in the kernel test
> >     robot's build test when HAVE_MOVE_PUD is enabled.
> >   - Keep WARN_ON_ONCE(1) instead of BUILD_BUG() for the aforementioned
> >     reason.
>
> Okay, but IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) on the caller side would
> do the trick, I believe.
I tried moving this to the caller side in move_page_tables(),
-                       if (extent == HPAGE_PMD_SIZE &&
+                       if (extent == HPAGE_PMD_SIZE &&
IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
but it produces the same error as reported by kernel test robot:
ld.lld: error: undefined symbol: move_huge_pmd
I'm not sure why these are different but the kernel test robot
compiler complains.
>
> >
> >  arch/Kconfig |   7 ++
> >  mm/mremap.c  | 220 ++++++++++++++++++++++++++++++++++++++++++++-------
> >  2 files changed, 197 insertions(+), 30 deletions(-)
> >
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index af14a567b493..5eabaa00bf9b 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -602,6 +602,13 @@ config HAVE_IRQ_TIME_ACCOUNTING
> >         Archs need to ensure they use a high enough resolution clock to
> >         support irq time accounting and then call enable_sched_clock_irqtime().
> >
> > +config HAVE_MOVE_PUD
> > +     bool
> > +     help
> > +       Architectures that select this are able to move page tables at the
> > +       PUD level. If there are only 3 page table levels, the move effectively
> > +       happens at the PGD level.
> > +
> >  config HAVE_MOVE_PMD
> >       bool
> >       help
> > diff --git a/mm/mremap.c b/mm/mremap.c
> > index 138abbae4f75..c1d6ab667d70 100644
> > --- a/mm/mremap.c
> > +++ b/mm/mremap.c
> > @@ -249,14 +249,176 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
> >
> >       return true;
> >  }
> > +#else
> > +static inline bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
> > +               unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
> > +{
> > +     return false;
> > +}
> >  #endif
> >
> > +#ifdef CONFIG_HAVE_MOVE_PUD
> > +static pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr)
> > +{
> > +     pgd_t *pgd;
> > +     p4d_t *p4d;
> > +     pud_t *pud;
> > +
> > +     pgd = pgd_offset(mm, addr);
> > +     if (pgd_none_or_clear_bad(pgd))
> > +             return NULL;
> > +
> > +     p4d = p4d_offset(pgd, addr);
> > +     if (p4d_none_or_clear_bad(p4d))
> > +             return NULL;
> > +
> > +     pud = pud_offset(p4d, addr);
> > +     if (pud_none_or_clear_bad(pud))
> > +             return NULL;
> > +
> > +     return pud;
> > +}
> > +
> > +static pud_t *alloc_new_pud(struct mm_struct *mm, struct vm_area_struct *vma,
> > +                         unsigned long addr)
> > +{
> > +     pgd_t *pgd;
> > +     p4d_t *p4d;
> > +     pud_t *pud;
> > +
> > +     pgd = pgd_offset(mm, addr);
> > +     p4d = p4d_alloc(mm, pgd, addr);
> > +     if (!p4d)
> > +             return NULL;
> > +     pud = pud_alloc(mm, p4d, addr);
> > +     if (!pud)
> > +             return NULL;
> > +
> > +     return pud;
> > +}
>
> Looks like a code duplication.
>
> Could you move these two helpers out of #ifdef CONFIG_HAVE_MOVE_PUD and
> make get_old_pmd() and alloc_new_pmd() use them?
Yes, that will be cleaner. I'll update it in the next version.
>
> > +
> > +static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
> > +               unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
> > +{
> > +     spinlock_t *old_ptl, *new_ptl;
> > +     struct mm_struct *mm = vma->vm_mm;
> > +     pud_t pud;
> > +
> > +     /*
> > +      * The destination pud shouldn't be established, free_pgtables()
> > +      * should have released it.
> > +      */
> > +     if (WARN_ON_ONCE(!pud_none(*new_pud)))
> > +             return false;
> > +
> > +     /*
> > +      * We don't have to worry about the ordering of src and dst
> > +      * ptlocks because exclusive mmap_lock prevents deadlock.
> > +      */
> > +     old_ptl = pud_lock(vma->vm_mm, old_pud);
> > +     new_ptl = pud_lockptr(mm, new_pud);
> > +     if (new_ptl != old_ptl)
> > +             spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
> > +
> > +     /* Clear the pud */
> > +     pud = *old_pud;
> > +     pud_clear(old_pud);
> > +
> > +     VM_BUG_ON(!pud_none(*new_pud));
> > +
> > +     /* Set the new pud */
> > +     set_pud_at(mm, new_addr, new_pud, pud);
> > +     flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE);
> > +     if (new_ptl != old_ptl)
> > +             spin_unlock(new_ptl);
> > +     spin_unlock(old_ptl);
> > +
> > +     return true;
> > +}
> > +#else
> > +static inline bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
> > +               unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
> > +{
> > +     return false;
> > +}
> > +#endif
> > +
> > +enum pgt_entry {
> > +     NORMAL_PMD,
> > +     HPAGE_PMD,
> > +     NORMAL_PUD,
> > +};
> > +
> > +/*
> > + * Returns an extent of the corresponding size for the pgt_entry specified if valid.
> > + * Else returns a smaller extent bounded by the end of the source and destination
> > + * pgt_entry. Returns 0 if an invalid pgt_entry is specified.
> > + */
> > +static unsigned long get_extent(enum pgt_entry entry, unsigned long old_addr,
> > +                     unsigned long old_end, unsigned long new_addr)
> > +{
> > +     unsigned long next, extent, mask, size;
> > +
> > +     if (entry == NORMAL_PMD || entry == HPAGE_PMD) {
> > +             mask = PMD_MASK;
> > +             size = PMD_SIZE;
> > +     } else if (entry == NORMAL_PUD) {
> > +             mask = PUD_MASK;
> > +             size = PUD_SIZE;
> > +     } else
> > +             return 0;
>
> Em. Who would ever specify invalid pgt_entry? It's bug.
> Again, switch()?
Sounds good. I'll use BUG() and switch() instead.
>
> > +
> > +     next = (old_addr + size) & mask;
> > +     /* even if next overflowed, extent below will be ok */
> > +     extent = (next > old_end) ? old_end - old_addr : next - old_addr;
> > +     next = (new_addr + size) & mask;
> > +     if (extent > next - new_addr)
> > +             extent = next - new_addr;
> > +     return extent;
> > +}
> > +
> > +/*
> > + * Attempts to speedup the move by moving entry at the level corresponding to
> > + * pgt_entry. Returns true if the move was successful, else false.
> > + */
> > +static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma,
> > +                     unsigned long old_addr, unsigned long new_addr, void *old_entry,
> > +                     void *new_entry, bool need_rmap_locks)
> > +{
> > +     bool moved = false;
> > +
> > +     /* See comment in move_ptes() */
> > +     if (need_rmap_locks)
> > +             take_rmap_locks(vma);
> > +
> > +     switch (entry) {
> > +     case NORMAL_PMD:
> > +             moved =  move_normal_pmd(vma, old_addr, new_addr, old_entry, new_entry);
>
> Nit: here and below, double space after '='. Why?
Sorry, editing mistake on my end. I'll clean this up before resending.
>
> > +             break;
> > +     case NORMAL_PUD:
> > +             moved =  move_normal_pud(vma, old_addr, new_addr, old_entry, new_entry);
> > +             break;
> > +     case HPAGE_PMD:
> > +             moved =  IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
> > +                     move_huge_pmd(vma, old_addr, new_addr, old_entry, new_entry);
> > +             break;
> > +     default:
> > +             WARN_ON_ONCE(1);
> > +             break;
> > +     }
> > +
> > +     if (need_rmap_locks)
> > +             drop_rmap_locks(vma);
> > +
> > +     return moved;
> > +}
> > +
> >  unsigned long move_page_tables(struct vm_area_struct *vma,
> >               unsigned long old_addr, struct vm_area_struct *new_vma,
> >               unsigned long new_addr, unsigned long len,
> >               bool need_rmap_locks)
> >  {
> > -     unsigned long extent, next, old_end;
> > +     unsigned long extent, old_end;
> >       struct mmu_notifier_range range;
> >       pmd_t *old_pmd, *new_pmd;
> >
> > @@ -269,14 +431,27 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
> >
> >       for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
> >               cond_resched();
> > -             next = (old_addr + PMD_SIZE) & PMD_MASK;
> > -             /* even if next overflowed, extent below will be ok */
> > -             extent = next - old_addr;
> > -             if (extent > old_end - old_addr)
> > -                     extent = old_end - old_addr;
> > -             next = (new_addr + PMD_SIZE) & PMD_MASK;
> > -             if (extent > next - new_addr)
> > -                     extent = next - new_addr;
> > +#ifdef CONFIG_HAVE_MOVE_PUD
>
> Any chance  if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD)) would work here?
Once we move get_old_put() and alloc_new_pud() out of the #ifdefs as
you suggested
above, it should work. It would also now be possible to replace the
#ifdef CONFIG_HAVE_MOVE_PMD in move_page_tables() with
IS_ENABLED(CONFIG_HAVE_MOVE_PMD).

Thanks,
Kalesh
>
> > +             /*
> > +              * If extent is PUD-sized try to speed up the move by moving at the
> > +              * PUD level if possible.
> > +              */
> > +             extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr);
> > +             if (extent == PUD_SIZE) {
> > +                     pud_t *old_pud, *new_pud;
> > +
> > +                     old_pud = get_old_pud(vma->vm_mm, old_addr);
> > +                     if (!old_pud)
> > +                             continue;
> > +                     new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr);
> > +                     if (!new_pud)
> > +                             break;
> > +                     if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr,
> > +                                        old_pud, new_pud, need_rmap_locks))
> > +                             continue;
> > +             }
> > +#endif
> > +             extent = get_extent(NORMAL_PMD, old_addr, old_end, new_addr);
> >               old_pmd = get_old_pmd(vma->vm_mm, old_addr);
> >               if (!old_pmd)
> >                       continue;
> > @@ -284,18 +459,10 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
> >               if (!new_pmd)
> >                       break;
> >               if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) || pmd_devmap(*old_pmd)) {
> > -                     if (extent == HPAGE_PMD_SIZE) {
> > -                             bool moved;
> > -                             /* See comment in move_ptes() */
> > -                             if (need_rmap_locks)
> > -                                     take_rmap_locks(vma);
> > -                             moved = move_huge_pmd(vma, old_addr, new_addr,
> > -                                                   old_pmd, new_pmd);
> > -                             if (need_rmap_locks)
> > -                                     drop_rmap_locks(vma);
> > -                             if (moved)
> > -                                     continue;
> > -                     }
> > +                     if (extent == HPAGE_PMD_SIZE &&
> > +                         move_pgt_entry(HPAGE_PMD, vma, old_addr, new_addr, old_pmd,
> > +                                        new_pmd, need_rmap_locks))
> > +                             continue;
> >                       split_huge_pmd(vma, old_pmd, old_addr);
> >                       if (pmd_trans_unstable(old_pmd))
> >                               continue;
> > @@ -305,15 +472,8 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
> >                        * If the extent is PMD-sized, try to speed the move by
> >                        * moving at the PMD level if possible.
> >                        */
> > -                     bool moved;
> > -
> > -                     if (need_rmap_locks)
> > -                             take_rmap_locks(vma);
> > -                     moved = move_normal_pmd(vma, old_addr, new_addr,
> > -                                             old_pmd, new_pmd);
> > -                     if (need_rmap_locks)
> > -                             drop_rmap_locks(vma);
> > -                     if (moved)
> > +                     if (move_pgt_entry(NORMAL_PMD, vma, old_addr, new_addr, old_pmd,
> > +                                        new_pmd, need_rmap_locks))
> >                               continue;
> >  #endif
> >               }
> > --
> > 2.28.0.806.g8561365e88-goog
> >
>
> --
>  Kirill A. Shutemov
>
> --
> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com.
>

Re: [PATCH v2 4/6] arm64: Add set_pud_at() function

[Kalesh Singh]

On Fri, Oct 2, 2020 at 12:52 PM Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> On Fri, Oct 02, 2020 at 04:20:49PM +0000, Kalesh Singh wrote:
> > set_pud_at() is used in move_normal_pud() for remapping
> > pages at the PUD level.
> >
> > Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
> > ---
> >  arch/arm64/include/asm/pgtable.h | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> > index d5d3fbe73953..8848125e3024 100644
> > --- a/arch/arm64/include/asm/pgtable.h
> > +++ b/arch/arm64/include/asm/pgtable.h
> > @@ -415,6 +415,7 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
> >  #define pfn_pud(pfn,prot)    __pud(__phys_to_pud_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
> >
> >  #define set_pmd_at(mm, addr, pmdp, pmd)      set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd))
> > +#define set_pud_at(mm, addr, pudp, pud)      set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud))
> >
> >  #define __p4d_to_phys(p4d)   __pte_to_phys(p4d_pte(p4d))
> >  #define __phys_to_p4d_val(phys)      __phys_to_pte_val(phys)
>
> Just fold it into the next patch.
Sounds good. I'll update in the next version. Thanks
>
> --
>  Kirill A. Shutemov
>
> --
> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com.
>

Re: [PATCH v2 3/6] mm: Speedup mremap on 1GB or larger regions

[Kalesh Singh]

On Fri, Oct 2, 2020 at 6:08 PM Kalesh Singh <kaleshsingh@google.com> wrote:
>
> Hi Kirill, thank you for the feedback.
>
> On Fri, Oct 2, 2020 at 12:51 PM Kirill A. Shutemov
> <kirill.shutemov@linux.intel.com> wrote:
> >
> > On Fri, Oct 02, 2020 at 04:20:48PM +0000, Kalesh Singh wrote:
> > > Android needs to move large memory regions for garbage collection.
> > > The GC requires moving physical pages of multi-gigabyte heap
> > > using mremap. During this move, the application threads have to
> > > be paused for correctness. It is critical to keep this pause as
> > > short as possible to avoid jitters during user interaction.
> > >
> > > Optimize mremap for >= 1GB-sized regions by moving at the PUD/PGD
> > > level if the source and destination addresses are PUD-aligned.
> > > For CONFIG_PGTABLE_LEVELS == 3, moving at the PUD level in effect moves
> > > PGD entries, since the PUD entry is “folded back” onto the PGD entry.
> > > Add HAVE_MOVE_PUD so that architectures where moving at the PUD level
> > > isn't supported/tested can turn this off by not selecting the config.
> > >
> > > Fix build test error from v1 of this series reported by
> > > kernel test robot in [1].
> > >
> > > [1] https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org/thread/CKPGL4FH4NG7TGH2CVYX2UX76L25BTA3/
> > >
> > > Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
> > > Reported-by: kernel test robot <lkp@intel.com>
> > > ---
> > > Changes in v2:
> > >   - Update commit message with description of Android GC's use case.
> > >   - Move set_pud_at() to a separate patch.
> > >   - Use switch() instead of ifs in move_pgt_entry()
> > >   - Fix build test error reported by kernel test robot on x86_64 in [1].
> > >     Guard move_huge_pmd() with IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE),
> > >     since this section doesn't get optimized out in the kernel test
> > >     robot's build test when HAVE_MOVE_PUD is enabled.
> > >   - Keep WARN_ON_ONCE(1) instead of BUILD_BUG() for the aforementioned
> > >     reason.
> >
> > Okay, but IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) on the caller side would
> > do the trick, I believe.
> I tried moving this to the caller side in move_page_tables(),
> -                       if (extent == HPAGE_PMD_SIZE &&
> +                       if (extent == HPAGE_PMD_SIZE &&
> IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
> but it produces the same error as reported by kernel test robot:
> ld.lld: error: undefined symbol: move_huge_pmd
> I'm not sure why these are different but the kernel test robot
> compiler complains.
I should mention also that the patch series compiles without having to
use IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) when using the test config
from kernel test robot’s report and clang --version:
Android (6443078 based on r383902) clang version 11.0.1
(https://android.googlesource.com/toolchain/llvm-project
b397f81060ce6d701042b782172ed13bee898b79)
> >
> > >
> > >  arch/Kconfig |   7 ++
> > >  mm/mremap.c  | 220 ++++++++++++++++++++++++++++++++++++++++++++-------
> > >  2 files changed, 197 insertions(+), 30 deletions(-)
> > >
> > > diff --git a/arch/Kconfig b/arch/Kconfig
> > > index af14a567b493..5eabaa00bf9b 100644
> > > --- a/arch/Kconfig
> > > +++ b/arch/Kconfig
> > > @@ -602,6 +602,13 @@ config HAVE_IRQ_TIME_ACCOUNTING
> > >         Archs need to ensure they use a high enough resolution clock to
> > >         support irq time accounting and then call enable_sched_clock_irqtime().
> > >
> > > +config HAVE_MOVE_PUD
> > > +     bool
> > > +     help
> > > +       Architectures that select this are able to move page tables at the
> > > +       PUD level. If there are only 3 page table levels, the move effectively
> > > +       happens at the PGD level.
> > > +
> > >  config HAVE_MOVE_PMD
> > >       bool
> > >       help
> > > diff --git a/mm/mremap.c b/mm/mremap.c
> > > index 138abbae4f75..c1d6ab667d70 100644
> > > --- a/mm/mremap.c
> > > +++ b/mm/mremap.c
> > > @@ -249,14 +249,176 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
> > >
> > >       return true;
> > >  }
> > > +#else
> > > +static inline bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
> > > +               unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
> > > +{
> > > +     return false;
> > > +}
> > >  #endif
> > >
> > > +#ifdef CONFIG_HAVE_MOVE_PUD
> > > +static pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr)
> > > +{
> > > +     pgd_t *pgd;
> > > +     p4d_t *p4d;
> > > +     pud_t *pud;
> > > +
> > > +     pgd = pgd_offset(mm, addr);
> > > +     if (pgd_none_or_clear_bad(pgd))
> > > +             return NULL;
> > > +
> > > +     p4d = p4d_offset(pgd, addr);
> > > +     if (p4d_none_or_clear_bad(p4d))
> > > +             return NULL;
> > > +
> > > +     pud = pud_offset(p4d, addr);
> > > +     if (pud_none_or_clear_bad(pud))
> > > +             return NULL;
> > > +
> > > +     return pud;
> > > +}
> > > +
> > > +static pud_t *alloc_new_pud(struct mm_struct *mm, struct vm_area_struct *vma,
> > > +                         unsigned long addr)
> > > +{
> > > +     pgd_t *pgd;
> > > +     p4d_t *p4d;
> > > +     pud_t *pud;
> > > +
> > > +     pgd = pgd_offset(mm, addr);
> > > +     p4d = p4d_alloc(mm, pgd, addr);
> > > +     if (!p4d)
> > > +             return NULL;
> > > +     pud = pud_alloc(mm, p4d, addr);
> > > +     if (!pud)
> > > +             return NULL;
> > > +
> > > +     return pud;
> > > +}
> >
> > Looks like a code duplication.
> >
> > Could you move these two helpers out of #ifdef CONFIG_HAVE_MOVE_PUD and
> > make get_old_pmd() and alloc_new_pmd() use them?
> Yes, that will be cleaner. I'll update it in the next version.
> >
> > > +
> > > +static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
> > > +               unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
> > > +{
> > > +     spinlock_t *old_ptl, *new_ptl;
> > > +     struct mm_struct *mm = vma->vm_mm;
> > > +     pud_t pud;
> > > +
> > > +     /*
> > > +      * The destination pud shouldn't be established, free_pgtables()
> > > +      * should have released it.
> > > +      */
> > > +     if (WARN_ON_ONCE(!pud_none(*new_pud)))
> > > +             return false;
> > > +
> > > +     /*
> > > +      * We don't have to worry about the ordering of src and dst
> > > +      * ptlocks because exclusive mmap_lock prevents deadlock.
> > > +      */
> > > +     old_ptl = pud_lock(vma->vm_mm, old_pud);
> > > +     new_ptl = pud_lockptr(mm, new_pud);
> > > +     if (new_ptl != old_ptl)
> > > +             spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
> > > +
> > > +     /* Clear the pud */
> > > +     pud = *old_pud;
> > > +     pud_clear(old_pud);
> > > +
> > > +     VM_BUG_ON(!pud_none(*new_pud));
> > > +
> > > +     /* Set the new pud */
> > > +     set_pud_at(mm, new_addr, new_pud, pud);
> > > +     flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE);
> > > +     if (new_ptl != old_ptl)
> > > +             spin_unlock(new_ptl);
> > > +     spin_unlock(old_ptl);
> > > +
> > > +     return true;
> > > +}
> > > +#else
> > > +static inline bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
> > > +               unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
> > > +{
> > > +     return false;
> > > +}
> > > +#endif
> > > +
> > > +enum pgt_entry {
> > > +     NORMAL_PMD,
> > > +     HPAGE_PMD,
> > > +     NORMAL_PUD,
> > > +};
> > > +
> > > +/*
> > > + * Returns an extent of the corresponding size for the pgt_entry specified if valid.
> > > + * Else returns a smaller extent bounded by the end of the source and destination
> > > + * pgt_entry. Returns 0 if an invalid pgt_entry is specified.
> > > + */
> > > +static unsigned long get_extent(enum pgt_entry entry, unsigned long old_addr,
> > > +                     unsigned long old_end, unsigned long new_addr)
> > > +{
> > > +     unsigned long next, extent, mask, size;
> > > +
> > > +     if (entry == NORMAL_PMD || entry == HPAGE_PMD) {
> > > +             mask = PMD_MASK;
> > > +             size = PMD_SIZE;
> > > +     } else if (entry == NORMAL_PUD) {
> > > +             mask = PUD_MASK;
> > > +             size = PUD_SIZE;
> > > +     } else
> > > +             return 0;
> >
> > Em. Who would ever specify invalid pgt_entry? It's bug.
> > Again, switch()?
> Sounds good. I'll use BUG() and switch() instead.
> >
> > > +
> > > +     next = (old_addr + size) & mask;
> > > +     /* even if next overflowed, extent below will be ok */
> > > +     extent = (next > old_end) ? old_end - old_addr : next - old_addr;
> > > +     next = (new_addr + size) & mask;
> > > +     if (extent > next - new_addr)
> > > +             extent = next - new_addr;
> > > +     return extent;
> > > +}
> > > +
> > > +/*
> > > + * Attempts to speedup the move by moving entry at the level corresponding to
> > > + * pgt_entry. Returns true if the move was successful, else false.
> > > + */
> > > +static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma,
> > > +                     unsigned long old_addr, unsigned long new_addr, void *old_entry,
> > > +                     void *new_entry, bool need_rmap_locks)
> > > +{
> > > +     bool moved = false;
> > > +
> > > +     /* See comment in move_ptes() */
> > > +     if (need_rmap_locks)
> > > +             take_rmap_locks(vma);
> > > +
> > > +     switch (entry) {
> > > +     case NORMAL_PMD:
> > > +             moved =  move_normal_pmd(vma, old_addr, new_addr, old_entry, new_entry);
> >
> > Nit: here and below, double space after '='. Why?
> Sorry, editing mistake on my end. I'll clean this up before resending.
> >
> > > +             break;
> > > +     case NORMAL_PUD:
> > > +             moved =  move_normal_pud(vma, old_addr, new_addr, old_entry, new_entry);
> > > +             break;
> > > +     case HPAGE_PMD:
> > > +             moved =  IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
> > > +                     move_huge_pmd(vma, old_addr, new_addr, old_entry, new_entry);
> > > +             break;
> > > +     default:
> > > +             WARN_ON_ONCE(1);
> > > +             break;
> > > +     }
> > > +
> > > +     if (need_rmap_locks)
> > > +             drop_rmap_locks(vma);
> > > +
> > > +     return moved;
> > > +}
> > > +
> > >  unsigned long move_page_tables(struct vm_area_struct *vma,
> > >               unsigned long old_addr, struct vm_area_struct *new_vma,
> > >               unsigned long new_addr, unsigned long len,
> > >               bool need_rmap_locks)
> > >  {
> > > -     unsigned long extent, next, old_end;
> > > +     unsigned long extent, old_end;
> > >       struct mmu_notifier_range range;
> > >       pmd_t *old_pmd, *new_pmd;
> > >
> > > @@ -269,14 +431,27 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
> > >
> > >       for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
> > >               cond_resched();
> > > -             next = (old_addr + PMD_SIZE) & PMD_MASK;
> > > -             /* even if next overflowed, extent below will be ok */
> > > -             extent = next - old_addr;
> > > -             if (extent > old_end - old_addr)
> > > -                     extent = old_end - old_addr;
> > > -             next = (new_addr + PMD_SIZE) & PMD_MASK;
> > > -             if (extent > next - new_addr)
> > > -                     extent = next - new_addr;
> > > +#ifdef CONFIG_HAVE_MOVE_PUD
> >
> > Any chance  if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD)) would work here?
> Once we move get_old_put() and alloc_new_pud() out of the #ifdefs as
> you suggested
> above, it should work. It would also now be possible to replace the
> #ifdef CONFIG_HAVE_MOVE_PMD in move_page_tables() with
> IS_ENABLED(CONFIG_HAVE_MOVE_PMD).
>
> Thanks,
> Kalesh
> >
> > > +             /*
> > > +              * If extent is PUD-sized try to speed up the move by moving at the
> > > +              * PUD level if possible.
> > > +              */
> > > +             extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr);
> > > +             if (extent == PUD_SIZE) {
> > > +                     pud_t *old_pud, *new_pud;
> > > +
> > > +                     old_pud = get_old_pud(vma->vm_mm, old_addr);
> > > +                     if (!old_pud)
> > > +                             continue;
> > > +                     new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr);
> > > +                     if (!new_pud)
> > > +                             break;
> > > +                     if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr,
> > > +                                        old_pud, new_pud, need_rmap_locks))
> > > +                             continue;
> > > +             }
> > > +#endif
> > > +             extent = get_extent(NORMAL_PMD, old_addr, old_end, new_addr);
> > >               old_pmd = get_old_pmd(vma->vm_mm, old_addr);
> > >               if (!old_pmd)
> > >                       continue;
> > > @@ -284,18 +459,10 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
> > >               if (!new_pmd)
> > >                       break;
> > >               if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) || pmd_devmap(*old_pmd)) {
> > > -                     if (extent == HPAGE_PMD_SIZE) {
> > > -                             bool moved;
> > > -                             /* See comment in move_ptes() */
> > > -                             if (need_rmap_locks)
> > > -                                     take_rmap_locks(vma);
> > > -                             moved = move_huge_pmd(vma, old_addr, new_addr,
> > > -                                                   old_pmd, new_pmd);
> > > -                             if (need_rmap_locks)
> > > -                                     drop_rmap_locks(vma);
> > > -                             if (moved)
> > > -                                     continue;
> > > -                     }
> > > +                     if (extent == HPAGE_PMD_SIZE &&
> > > +                         move_pgt_entry(HPAGE_PMD, vma, old_addr, new_addr, old_pmd,
> > > +                                        new_pmd, need_rmap_locks))
> > > +                             continue;
> > >                       split_huge_pmd(vma, old_pmd, old_addr);
> > >                       if (pmd_trans_unstable(old_pmd))
> > >                               continue;
> > > @@ -305,15 +472,8 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
> > >                        * If the extent is PMD-sized, try to speed the move by
> > >                        * moving at the PMD level if possible.
> > >                        */
> > > -                     bool moved;
> > > -
> > > -                     if (need_rmap_locks)
> > > -                             take_rmap_locks(vma);
> > > -                     moved = move_normal_pmd(vma, old_addr, new_addr,
> > > -                                             old_pmd, new_pmd);
> > > -                     if (need_rmap_locks)
> > > -                             drop_rmap_locks(vma);
> > > -                     if (moved)
> > > +                     if (move_pgt_entry(NORMAL_PMD, vma, old_addr, new_addr, old_pmd,
> > > +                                        new_pmd, need_rmap_locks))
> > >                               continue;
> > >  #endif
> > >               }
> > > --
> > > 2.28.0.806.g8561365e88-goog
> > >
> >
> > --
> >  Kirill A. Shutemov
> >
> > --
> > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com.
> >

Re: [PATCH v2 1/6] kselftests: vm: Add mremap tests

[Kalesh Singh]

On Sat, Oct 3, 2020 at 3:13 AM John Hubbard <jhubbard@nvidia.com> wrote:
>
> On 10/2/20 9:20 AM, Kalesh Singh wrote:
> > Test mremap on regions of various sizes and alignments and validate
> > data after remapping. Also provide total time for remapping
> > the region which is useful for performance comparison of the mremap
> > optimizations that move pages at the PMD/PUD levels if HAVE_MOVE_PMD
> > and/or HAVE_MOVE_PUD are enabled.
> >
> > Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
> > ---
> > Changes in v2:
> >    - Reduce test time by only validating a certain threshold of the
> >      remapped region (4MB by default). The -t flag can be used to
> >      set a custom threshold in MB or no threshold by passing 0. (-t0).
> >      mremap time is not provided in stdout for only partially validated
> >      regions. This time is only applicable for comparison if the entire
> >      mapped region was faulted in.
> >    - Use a random pattern for validating the remapped region. The -p
> >      flag can be used to run the tests with a specified seed for the
> >      random pattern.
> >    - Print test configs (threshold_mb and pattern_seed) to stdout.
> >    - Remove MAKE_SIMPLE_TEST macro.
> >    - Define named flags instead of 0 / 1.
> >    - Add comments for destination address' align_mask and offset.
>
> Thanks for making those changes. This all looks much nicer, both in the
> code and on the screen. Now it's easy to see which code generates which
> output, and the tests are readable. The new comments are also helpful.
>
> I ran it locally and it came in at 0.6 sec, so that looks good.
>
> A remaining nit: there are lots of > 80 col lines here. Only those lines
> that contain printf output strings really need to be extra-long. The
> others can all be easily made to fit.
Thanks for the review John. I can fix the lines that don't need to be
>80 col. FWIW checkpatch now allows 100 col lines:
https://lore.kernel.org/r/9c360bfa43580ce7726dd3d9d247f1216a690ef0.camel@perches.com
>
> ...
> > +
> > +#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
> > +#define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
>
>
> Not really a comment on this patch, but: at least two other test suites
> in selftests/ have had to recreate MIN() or min(), and probably a few
> other common things as well. It would be nice to gather up some of these
> common things into one of the shared header files in selftests/.
>
> I'm certainly not saying that this patchset has that responsibility,
> though. Just pointing it out in case someone has a moment to clean up a
> few here and there.
Thanks for pointing this out. I'll leave it as a task for a separate
patch if time permits or no one gets around to it before :-)
>
> I'll assume that any changes to make things fit within 80 cols are
> trivial, so you can add:
>
> Reviewed-by: John Hubbard <jhubbard@nvidia.com>
>
> thanks,
> --
> John Hubbard
> NVIDIA
>
> > +
> > +struct config {
> > +     unsigned long long src_alignment;
> > +     unsigned long long dest_alignment;
> > +     unsigned long long region_size;
> > +     int overlapping;
> > +};
> > +
> > +struct test {
> > +     const char *name;
> > +     struct config config;
> > +     int expect_failure;
> > +};
> > +
> > +enum {
> > +     _1KB = 1ULL << 10,      /* 1KB -> not page aligned */
> > +     _4KB = 4ULL << 10,
> > +     _8KB = 8ULL << 10,
> > +     _1MB = 1ULL << 20,
> > +     _2MB = 2ULL << 20,
> > +     _4MB = 4ULL << 20,
> > +     _1GB = 1ULL << 30,
> > +     _2GB = 2ULL << 30,
> > +     PTE = _4KB,
> > +     PMD = _2MB,
> > +     PUD = _1GB,
> > +};
> > +
> > +#define MAKE_TEST(source_align, destination_align, size,     \
> > +               overlaps, should_fail, test_name)             \
> > +{                                                            \
> > +     .name = test_name,                                      \
> > +     .config = {                                             \
> > +             .src_alignment = source_align,                  \
> > +             .dest_alignment = destination_align,            \
> > +             .region_size = size,                            \
> > +             .overlapping = overlaps,                        \
> > +     },                                                      \
> > +     .expect_failure = should_fail                           \
> > +}
> > +
> > +/*
> > + * Returns the start address of the mapping on success, else returns
> > + * NULL on failure.
> > + */
> > +static void *get_source_mapping(struct config c)
> > +{
> > +     unsigned long long addr = 0ULL;
> > +     void *src_addr = NULL;
> > +retry:
> > +     addr += c.src_alignment;
> > +     src_addr = mmap((void *) addr, c.region_size, PROT_READ | PROT_WRITE,
> > +                     MAP_FIXED | MAP_ANONYMOUS | MAP_SHARED, -1, 0);
> > +     if (src_addr == MAP_FAILED) {
> > +             if (errno == EPERM)
> > +                     goto retry;
> > +             goto error;
> > +     }
> > +     /*
> > +      * Check that the address is aligned to the specified alignment. Addresses
> > +      * which have alignments that are multiples of that specified are not considered
> > +      * valid. For instance, 1GB address is 2MB-aligned, however it will not be
> > +      * considered valid for a requested alignment of 2MB. This is done to
> > +      * reduce coincidental alignment in the tests.
> > +      */
> > +     if (((unsigned long long) src_addr & (c.src_alignment - 1)) ||
> > +                     !((unsigned long long) src_addr & c.src_alignment))
> > +             goto retry;
> > +
> > +     if (!src_addr)
> > +             goto error;
> > +
> > +     return src_addr;
> > +error:
> > +     ksft_print_msg("Failed to map source region: %s\n",
> > +                     strerror(errno));
> > +     return NULL;
> > +}
> > +
> > +/* Returns the time taken for the remap on success else returns -1. */
> > +static long long remap_region(struct config c, unsigned int threshold_mb,
> > +                           char pattern_seed)
> > +{
> > +     void *addr, *src_addr, *dest_addr;
> > +     unsigned long long i;
> > +     struct timespec t_start = {0, 0}, t_end = {0, 0};
> > +     long long  start_ns, end_ns, align_mask, ret, offset;
> > +     unsigned long long threshold;
> > +
> > +     if (threshold_mb == VALIDATION_NO_THRESHOLD)
> > +             threshold = c.region_size;
> > +     else
> > +             threshold = MIN(threshold_mb * _1MB, c.region_size);
> > +
> > +     src_addr = get_source_mapping(c);
> > +     if (!src_addr) {
> > +             ret = -1;
> > +             goto out;
> > +     }
> > +
> > +     /* Set byte pattern */
> > +     srand(pattern_seed);
> > +     for (i = 0; i < threshold; i++)
> > +             memset((char *) src_addr + i, (char) rand(), 1);
> > +
> > +     /* Mask to zero out lower bits of address for alignment */
> > +     align_mask = ~(c.dest_alignment - 1);
> > +     /* Offset of destination address from the end of the source region */
> > +     offset = (c.overlapping) ? -c.dest_alignment : c.dest_alignment;
> > +     addr = (void *) (((unsigned long long) src_addr + c.region_size + offset)
> > +                     & align_mask);
> > +
> > +     /* See comment in get_source_mapping() */
> > +     if (!((unsigned long long) addr & c.dest_alignment))
> > +             addr = (void *) ((unsigned long long) addr | c.dest_alignment);
> > +
> > +     clock_gettime(CLOCK_MONOTONIC, &t_start);
> > +     dest_addr = mremap(src_addr, c.region_size, c.region_size,
> > +                     MREMAP_MAYMOVE|MREMAP_FIXED, (char *) addr);
> > +     clock_gettime(CLOCK_MONOTONIC, &t_end);
> > +
> > +     if (dest_addr == MAP_FAILED) {
> > +             ksft_print_msg("mremap failed: %s\n", strerror(errno));
> > +             ret = -1;
> > +             goto clean_up_src;
> > +     }
> > +
> > +     /* Verify byte pattern after remapping */
> > +     srand(pattern_seed);
> > +     for (i = 0; i < threshold; i++) {
> > +             char c = (char) rand();
> > +
> > +             if (((char *) dest_addr)[i] != c) {
> > +                     ksft_print_msg("Data after remap doesn't match at offset %d\n",
> > +                                     i);
> > +                     ksft_print_msg("Expected: %#x\t Got: %#x\n", c & 0xff,
> > +                                     ((char *) dest_addr)[i] & 0xff);
> > +                     ret = -1;
> > +                     goto clean_up_dest;
> > +             }
> > +     }
> > +
> > +     start_ns = t_start.tv_sec * NS_PER_SEC + t_start.tv_nsec;
> > +     end_ns = t_end.tv_sec * NS_PER_SEC + t_end.tv_nsec;
> > +     ret = end_ns - start_ns;
> > +
> > +/*
> > + * Since the destination address is specified using MREMAP_FIXED, subsequent mremap will unmap any
> > + * previous mapping at the address range specified by dest_addr and region_size. This significantly
> > + * affects the remap time of subsequent tests. So we clean up mappings after each test.
> > + */
> > +clean_up_dest:
> > +     munmap(dest_addr, c.region_size);
> > +clean_up_src:
> > +     munmap(src_addr, c.region_size);
> > +out:
> > +     return ret;
> > +}
> > +
> > +static void run_mremap_test_case(struct test test_case, int *failures, unsigned int threshold_mb,
> > +                              unsigned int pattern_seed)
> > +{
> > +     long long remap_time = remap_region(test_case.config, threshold_mb, pattern_seed);
> > +
> > +     if (remap_time < 0) {
> > +             if (test_case.expect_failure)
> > +                     ksft_test_result_pass("%s\n\tExpected mremap failure\n", test_case.name);
> > +             else {
> > +                     ksft_test_result_fail("%s\n", test_case.name);
> > +                     *failures += 1;
> > +             }
> > +     } else {
> > +             /* Comparing mremap time is only applicable if entire region was faulted in */
> > +             if (threshold_mb == VALIDATION_NO_THRESHOLD ||
> > +                 test_case.config.region_size <= threshold_mb * _1MB)
> > +                     ksft_test_result_pass("%s\n\tmremap time: %12lldns\n",
> > +                                           test_case.name, remap_time);
> > +             else
> > +                     ksft_test_result_pass("%s\n", test_case.name);
> > +     }
> > +}
> > +
> > +static void usage(const char *cmd)
> > +{
> > +     fprintf(stderr,
> > +             "Usage: %s [[-t <threshold_mb>] [-p <pattern_seed>]]\n"
> > +             "-t\t only validate threshold_mb of the remapped region\n"
> > +             "  \t if 0 is supplied no threshold is used; all tests\n"
> > +             "  \t are run and remapped regions validated fully.\n"
> > +             "  \t The default threshold used is 4MB.\n"
> > +             "-p\t provide a seed to generate the random pattern for\n"
> > +             "  \t validating the remapped region.\n", cmd);
> > +}
> > +
> > +static int parse_args(int argc, char **argv, unsigned int *threshold_mb,
> > +                   unsigned int *pattern_seed)
> > +{
> > +     const char *optstr = "t:p:";
> > +     int opt;
> > +
> > +     while ((opt = getopt(argc, argv, optstr)) != -1) {
> > +             switch (opt) {
> > +             case 't':
> > +                     *threshold_mb = atoi(optarg);
> > +                     break;
> > +             case 'p':
> > +                     *pattern_seed = atoi(optarg);
> > +                     break;
> > +             default:
> > +                     usage(argv[0]);
> > +                     return -1;
> > +             }
> > +     }
> > +
> > +     if (optind < argc) {
> > +             usage(argv[0]);
> > +             return -1;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +int main(int argc, char **argv)
> > +{
> > +     int failures = 0;
> > +     int i, run_perf_tests;
> > +     unsigned int threshold_mb = VALIDATION_DEFAULT_THRESHOLD;
> > +     unsigned int pattern_seed;
> > +     time_t t;
> > +
> > +     pattern_seed = (unsigned int) time(&t);
> > +
> > +     if (parse_args(argc, argv, &threshold_mb, &pattern_seed) < 0)
> > +             exit(EXIT_FAILURE);
> > +
> > +     ksft_print_msg("Test configs:\n\tthreshold_mb=%u\n\tpattern_seed=%u\n\n",
> > +                    threshold_mb, pattern_seed);
> > +
> > +     struct test test_cases[] = {
> > +             /* Expected mremap failures */
> > +             MAKE_TEST(_4KB, _4KB, _4KB, OVERLAPPING, EXPECT_FAILURE,
> > +                       "mremap - Source and Destination Regions Overlapping"),
> > +             MAKE_TEST(_4KB, _1KB, _4KB, NON_OVERLAPPING, EXPECT_FAILURE,
> > +                       "mremap - Destination Address Misaligned (1KB-aligned)"),
> > +             MAKE_TEST(_1KB, _4KB, _4KB, NON_OVERLAPPING, EXPECT_FAILURE,
> > +                       "mremap - Source Address Misaligned (1KB-aligned)"),
> > +
> > +             /* Src addr PTE aligned */
> > +             MAKE_TEST(PTE, PTE, _8KB, NON_OVERLAPPING, EXPECT_SUCCESS,
> > +                       "8KB mremap - Source PTE-aligned, Destination PTE-aligned"),
> > +
> > +             /* Src addr 1MB aligned */
> > +             MAKE_TEST(_1MB, PTE, _2MB, NON_OVERLAPPING, EXPECT_SUCCESS,
> > +                       "2MB mremap - Source 1MB-aligned, Destination PTE-aligned"),
> > +             MAKE_TEST(_1MB, _1MB, _2MB, NON_OVERLAPPING, EXPECT_SUCCESS,
> > +                       "2MB mremap - Source 1MB-aligned, Destination 1MB-aligned"),
> > +
> > +             /* Src addr PMD aligned */
> > +             MAKE_TEST(PMD, PTE, _4MB, NON_OVERLAPPING, EXPECT_SUCCESS,
> > +                       "4MB mremap - Source PMD-aligned, Destination PTE-aligned"),
> > +             MAKE_TEST(PMD, _1MB, _4MB, NON_OVERLAPPING, EXPECT_SUCCESS,
> > +                       "4MB mremap - Source PMD-aligned, Destination 1MB-aligned"),
> > +             MAKE_TEST(PMD, PMD, _4MB, NON_OVERLAPPING, EXPECT_SUCCESS,
> > +                       "4MB mremap - Source PMD-aligned, Destination PMD-aligned"),
> > +
> > +             /* Src addr PUD aligned */
> > +             MAKE_TEST(PUD, PTE, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> > +                       "2GB mremap - Source PUD-aligned, Destination PTE-aligned"),
> > +             MAKE_TEST(PUD, _1MB, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> > +                       "2GB mremap - Source PUD-aligned, Destination 1MB-aligned"),
> > +             MAKE_TEST(PUD, PMD, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> > +                       "2GB mremap - Source PUD-aligned, Destination PMD-aligned"),
> > +             MAKE_TEST(PUD, PUD, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> > +                       "2GB mremap - Source PUD-aligned, Destination PUD-aligned"),
> > +     };
> > +
> > +     struct test perf_test_cases[] = {
> > +             /* mremap 1GB region - Page table level aligned time comparison */
> > +             MAKE_TEST(PTE, PTE, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> > +                       "1GB mremap - Source PTE-aligned, Destination PTE-aligned"),
> > +             MAKE_TEST(PMD, PMD, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> > +                       "1GB mremap - Source PMD-aligned, Destination PMD-aligned"),
> > +             MAKE_TEST(PUD, PUD, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> > +                       "1GB mremap - Source PUD-aligned, Destination PUD-aligned"),
> > +     };
> > +
> > +     run_perf_tests =  (threshold_mb == VALIDATION_NO_THRESHOLD) ||
> > +                             (threshold_mb * _1MB >= _1GB);
> > +
> > +     ksft_set_plan(ARRAY_SIZE(test_cases) + (run_perf_tests ?
> > +                   ARRAY_SIZE(perf_test_cases) : 0));
> > +
> > +     for (i = 0; i < ARRAY_SIZE(test_cases); i++)
> > +             run_mremap_test_case(test_cases[i], &failures, threshold_mb, pattern_seed);
> > +
> > +     if (run_perf_tests) {
> > +             ksft_print_msg("\n%s\n",
> > +              "mremap HAVE_MOVE_PMD/PUD optimization time comparison for 1GB region:");
> > +             for (i = 0; i < ARRAY_SIZE(perf_test_cases); i++)
> > +                     run_mremap_test_case(perf_test_cases[i], &failures, threshold_mb,
> > +                                          pattern_seed);
> > +     }
> > +
> > +     if (failures > 0)
> > +             ksft_exit_fail();
> > +     else
> > +             ksft_exit_pass();
> > +}
> > diff --git a/tools/testing/selftests/vm/run_vmtests b/tools/testing/selftests/vm/run_vmtests
> > index a3f4f30f0a2e..d578ad831813 100755
> > --- a/tools/testing/selftests/vm/run_vmtests
> > +++ b/tools/testing/selftests/vm/run_vmtests
> > @@ -241,6 +241,17 @@ else
> >       echo "[PASS]"
> >   fi
> >
> > +echo "-------------------"
> > +echo "running mremap_test"
> > +echo "-------------------"
> > +./mremap_test
> > +if [ $? -ne 0 ]; then
> > +     echo "[FAIL]"
> > +     exitcode=1
> > +else
> > +     echo "[PASS]"
> > +fi
> > +
> >   echo "-----------------"
> >   echo "running thuge-gen"
> >   echo "-----------------"
> >
>
> --
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