From: "Maciej W. Rozycki" <macro@orcam.me.uk>
To: Arnd Bergmann <arnd@arndb.de>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Huacai Chen <chenhuacai@kernel.org>,
Huacai Chen <chenhuacai@loongson.cn>,
Jiaxun Yang <jiaxun.yang@flygoat.com>,
linux-arch@vger.kernel.org, linux-mips@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 1/4] lib/math: Add a `do_div' test module
Date: Tue, 20 Apr 2021 04:50:28 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.2104200113290.44318@angie.orcam.me.uk> (raw)
In-Reply-To: <alpine.DEB.2.21.2104200044060.44318@angie.orcam.me.uk>
Implement a module for correctness and performance evaluation for the
`do_div' function, often handled in an optimised manner by platform
code. Use a somewhat randomly generated set of inputs that is supposed
to be representative, using the same set of divisors twice, expressed as
a constant and as a variable each, so as to verify the implementation
for both cases should they be handled by different code execution paths.
Reference results were produced with GNU bc.
At the conclusion output the total execution time elapsed.
Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
---
NB there's a `checkpatch.pl' warning for a split line, but I can see no
gain from joining it.
---
lib/Kconfig.debug | 10 ++
lib/math/Makefile | 2
lib/math/test_div64.c | 249 ++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 261 insertions(+)
linux-div64-test.diff
Index: linux-3maxp-div64/lib/Kconfig.debug
===================================================================
--- linux-3maxp-div64.orig/lib/Kconfig.debug
+++ linux-3maxp-div64/lib/Kconfig.debug
@@ -2027,6 +2027,16 @@ config TEST_SORT
If unsure, say N.
+config TEST_DIV64
+ tristate "64bit/32bit division and modulo test"
+ depends on DEBUG_KERNEL || m
+ help
+ Enable this to turn on 'do_div()' function test. This test is
+ executed only once during system boot (so affects only boot time),
+ or at module load time.
+
+ If unsure, say N.
+
config KPROBES_SANITY_TEST
bool "Kprobes sanity tests"
depends on DEBUG_KERNEL
Index: linux-3maxp-div64/lib/math/Makefile
===================================================================
--- linux-3maxp-div64.orig/lib/math/Makefile
+++ linux-3maxp-div64/lib/math/Makefile
@@ -4,3 +4,5 @@ obj-y += div64.o gcd.o lcm.o int_pow.o i
obj-$(CONFIG_CORDIC) += cordic.o
obj-$(CONFIG_PRIME_NUMBERS) += prime_numbers.o
obj-$(CONFIG_RATIONAL) += rational.o
+
+obj-$(CONFIG_TEST_DIV64) += test_div64.o
Index: linux-3maxp-div64/lib/math/test_div64.c
===================================================================
--- /dev/null
+++ linux-3maxp-div64/lib/math/test_div64.c
@@ -0,0 +1,249 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 Maciej W. Rozycki
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/ktime.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/time64.h>
+#include <linux/types.h>
+
+#include <asm/div64.h>
+
+#define TEST_DIV64_N_ITER 1024
+
+static const u64 test_div64_dividents[] = {
+ 0x00000000ab275080,
+ 0x0000000fe73c1959,
+ 0x000000e54c0a74b1,
+ 0x00000d4398ff1ef9,
+ 0x0000a18c2ee1c097,
+ 0x00079fb80b072e4a,
+ 0x0072db27380dd689,
+ 0x0842f488162e2284,
+ 0xf66745411d8ab063,
+};
+#define SIZE_DIV64_DIVIDENTS ARRAY_SIZE(test_div64_dividents)
+
+#define TEST_DIV64_DIVISOR_0 0x00000009
+#define TEST_DIV64_DIVISOR_1 0x0000007c
+#define TEST_DIV64_DIVISOR_2 0x00000204
+#define TEST_DIV64_DIVISOR_3 0x0000cb5b
+#define TEST_DIV64_DIVISOR_4 0x00010000
+#define TEST_DIV64_DIVISOR_5 0x0008a880
+#define TEST_DIV64_DIVISOR_6 0x003fd3ae
+#define TEST_DIV64_DIVISOR_7 0x0b658fac
+#define TEST_DIV64_DIVISOR_8 0xdc08b349
+
+static const u32 test_div64_divisors[] = {
+ TEST_DIV64_DIVISOR_0,
+ TEST_DIV64_DIVISOR_1,
+ TEST_DIV64_DIVISOR_2,
+ TEST_DIV64_DIVISOR_3,
+ TEST_DIV64_DIVISOR_4,
+ TEST_DIV64_DIVISOR_5,
+ TEST_DIV64_DIVISOR_6,
+ TEST_DIV64_DIVISOR_7,
+ TEST_DIV64_DIVISOR_8,
+};
+#define SIZE_DIV64_DIVISORS ARRAY_SIZE(test_div64_divisors)
+
+static const struct {
+ u64 quotient;
+ u32 remainder;
+} test_div64_results[SIZE_DIV64_DIVISORS][SIZE_DIV64_DIVIDENTS] = {
+ {
+ { 0x0000000013045e47, 0x00000001 },
+ { 0x000000000161596c, 0x00000030 },
+ { 0x000000000054e9d4, 0x00000130 },
+ { 0x000000000000d776, 0x0000278e },
+ { 0x000000000000ab27, 0x00005080 },
+ { 0x00000000000013c4, 0x0004ce80 },
+ { 0x00000000000002ae, 0x001e143c },
+ { 0x000000000000000f, 0x0033e56c },
+ { 0x0000000000000000, 0xab275080 },
+ }, {
+ { 0x00000001c45c02d1, 0x00000000 },
+ { 0x0000000020d5213c, 0x00000049 },
+ { 0x0000000007e3d65f, 0x000001dd },
+ { 0x0000000000140531, 0x000065ee },
+ { 0x00000000000fe73c, 0x00001959 },
+ { 0x000000000001d637, 0x0004e5d9 },
+ { 0x0000000000003fc9, 0x000713bb },
+ { 0x0000000000000165, 0x029abe7d },
+ { 0x0000000000000012, 0x6e9f7e37 },
+ }, {
+ { 0x000000197a3a0cf7, 0x00000002 },
+ { 0x00000001d9632e5c, 0x00000021 },
+ { 0x0000000071c28039, 0x000001cd },
+ { 0x000000000120a844, 0x0000b885 },
+ { 0x0000000000e54c0a, 0x000074b1 },
+ { 0x00000000001a7bb3, 0x00072331 },
+ { 0x00000000000397ad, 0x0002c61b },
+ { 0x000000000000141e, 0x06ea2e89 },
+ { 0x000000000000010a, 0xab002ad7 },
+ }, {
+ { 0x0000017949e37538, 0x00000001 },
+ { 0x0000001b62441f37, 0x00000055 },
+ { 0x0000000694a3391d, 0x00000085 },
+ { 0x0000000010b2a5d2, 0x0000a753 },
+ { 0x000000000d4398ff, 0x00001ef9 },
+ { 0x0000000001882ec6, 0x0005cbf9 },
+ { 0x000000000035333b, 0x0017abdf },
+ { 0x00000000000129f1, 0x0ab4520d },
+ { 0x0000000000000f6e, 0x8ac0ce9b },
+ }, {
+ { 0x000011f321a74e49, 0x00000006 },
+ { 0x0000014d8481d211, 0x0000005b },
+ { 0x0000005025cbd92d, 0x000001e3 },
+ { 0x00000000cb5e71e3, 0x000043e6 },
+ { 0x00000000a18c2ee1, 0x0000c097 },
+ { 0x0000000012a88828, 0x00036c97 },
+ { 0x000000000287f16f, 0x002c2a25 },
+ { 0x00000000000e2cc7, 0x02d581e3 },
+ { 0x000000000000bbf4, 0x1ba08c03 },
+ }, {
+ { 0x0000d8db8f72935d, 0x00000005 },
+ { 0x00000fbd5aed7a2e, 0x00000002 },
+ { 0x000003c84b6ea64a, 0x00000122 },
+ { 0x0000000998fa8829, 0x000044b7 },
+ { 0x000000079fb80b07, 0x00002e4a },
+ { 0x00000000e16b20fa, 0x0002a14a },
+ { 0x000000001e940d22, 0x00353b2e },
+ { 0x0000000000ab40ac, 0x06fba6ba },
+ { 0x000000000008debd, 0x72d98365 },
+ }, {
+ { 0x000cc3045b8fc281, 0x00000000 },
+ { 0x0000ed1f48b5c9fc, 0x00000079 },
+ { 0x000038fb9c63406a, 0x000000e1 },
+ { 0x000000909705b825, 0x00000a62 },
+ { 0x00000072db27380d, 0x0000d689 },
+ { 0x0000000d43fce827, 0x00082b09 },
+ { 0x00000001ccaba11a, 0x0037e8dd },
+ { 0x000000000a13f729, 0x0566dffd },
+ { 0x000000000085a14b, 0x23d36726 },
+ }, {
+ { 0x00eafeb9c993592b, 0x00000001 },
+ { 0x00110e5befa9a991, 0x00000048 },
+ { 0x00041947b4a1d36a, 0x000000dc },
+ { 0x00000a6679327311, 0x0000c079 },
+ { 0x00000842f488162e, 0x00002284 },
+ { 0x000000f4459740fc, 0x00084484 },
+ { 0x0000002122c47bf9, 0x002ca446 },
+ { 0x00000000b9936290, 0x004979c4 },
+ { 0x00000000099ca89d, 0x9db446bf },
+ }, {
+ { 0x1b60cece589da1d2, 0x00000001 },
+ { 0x01fcb42be1453f5b, 0x0000004f },
+ { 0x007a3f2457df0749, 0x0000013f },
+ { 0x0001363130e3ec7b, 0x000017aa },
+ { 0x0000f66745411d8a, 0x0000b063 },
+ { 0x00001c757dfab350, 0x00048863 },
+ { 0x000003dc4979c652, 0x00224ea7 },
+ { 0x000000159edc3144, 0x06409ab3 },
+ { 0x000000011eadfee3, 0xa99c48a8 },
+ },
+};
+
+static inline bool test_div64_verify(u64 quotient, u32 remainder, int i, int j)
+{
+ return (quotient == test_div64_results[i][j].quotient &&
+ remainder == test_div64_results[i][j].remainder);
+}
+
+/*
+ * This needs to be a macro, because we don't want to rely on the compiler
+ * to do constant propagation, and `do_div' may take a different path for
+ * constants, so we do want to verify that as well.
+ */
+#define test_div64_one(divident, divisor, i, j) ({ \
+ bool result = true; \
+ u64 quotient; \
+ u32 remainder; \
+ \
+ quotient = divident; \
+ remainder = do_div(quotient, divisor); \
+ if (!test_div64_verify(quotient, remainder, i, j)) { \
+ pr_err("ERROR: %016llx / %08x => %016llx,%08x\n", \
+ divident, divisor, quotient, remainder); \
+ pr_err("ERROR: expected value=> %016llx,%08x\n", \
+ test_div64_results[i][j].quotient, \
+ test_div64_results[i][j].remainder); \
+ result = false; \
+ } \
+ result; \
+})
+
+/*
+ * Run calculation for the same divisor value expressed as a constant
+ * and as a variable, so as to verify the implementation for both cases
+ * should they be handled by different code execution paths.
+ */
+static bool __init test_div64(void)
+{
+ u64 divident;
+ int i, j;
+
+ for (i = 0; i < SIZE_DIV64_DIVIDENTS; i++) {
+ divident = test_div64_dividents[i];
+ if (!test_div64_one(divident, TEST_DIV64_DIVISOR_0, i, 0))
+ return false;
+ if (!test_div64_one(divident, TEST_DIV64_DIVISOR_1, i, 1))
+ return false;
+ if (!test_div64_one(divident, TEST_DIV64_DIVISOR_2, i, 2))
+ return false;
+ if (!test_div64_one(divident, TEST_DIV64_DIVISOR_3, i, 3))
+ return false;
+ if (!test_div64_one(divident, TEST_DIV64_DIVISOR_4, i, 4))
+ return false;
+ if (!test_div64_one(divident, TEST_DIV64_DIVISOR_5, i, 5))
+ return false;
+ if (!test_div64_one(divident, TEST_DIV64_DIVISOR_6, i, 6))
+ return false;
+ if (!test_div64_one(divident, TEST_DIV64_DIVISOR_7, i, 7))
+ return false;
+ if (!test_div64_one(divident, TEST_DIV64_DIVISOR_8, i, 8))
+ return false;
+ for (j = 0; j < SIZE_DIV64_DIVISORS; j++) {
+ if (!test_div64_one(divident, test_div64_divisors[j],
+ i, j))
+ return false;
+ }
+ }
+ return true;
+}
+
+static int __init test_div64_init(void)
+{
+ struct timespec64 ts, ts0, ts1;
+ int i;
+
+ pr_info("Starting 64bit/32bit division and modulo test\n");
+ ktime_get_ts64(&ts0);
+
+ for (i = 0; i < TEST_DIV64_N_ITER; i++)
+ if (!test_div64())
+ break;
+
+ ktime_get_ts64(&ts1);
+ ts = timespec64_sub(ts1, ts0);
+ pr_info("Completed 64bit/32bit division and modulo test, "
+ "%llu.%09lus elapsed\n", ts.tv_sec, ts.tv_nsec);
+
+ return 0;
+}
+
+static void __exit test_div64_exit(void)
+{
+}
+
+module_init(test_div64_init);
+module_exit(test_div64_exit);
+
+MODULE_AUTHOR("Maciej W. Rozycki <macro@orcam.me.uk>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("64bit/32bit division and modulo test module");
next prev parent reply other threads:[~2021-04-20 2:50 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-20 2:50 [PATCH 0/4] Reinstate and improve MIPS `do_div' implementation Maciej W. Rozycki
2021-04-20 2:50 ` Maciej W. Rozycki [this message]
2021-04-20 2:50 ` [PATCH 2/4] div64: Correct inline documentation for `do_div' Maciej W. Rozycki
2021-04-20 2:50 ` [PATCH 3/4] MIPS: Reinstate platform `__div64_32' handler Maciej W. Rozycki
2021-04-22 18:36 ` Guenter Roeck
2021-04-22 20:43 ` Maciej W. Rozycki
2021-04-20 2:50 ` [PATCH 4/4] MIPS: Avoid DIVU in `__div64_32' is result would be zero Maciej W. Rozycki
2021-04-21 16:05 ` H. Nikolaus Schaller
2021-04-21 16:16 ` Maciej W. Rozycki
2021-04-22 7:56 ` Thomas Bogendoerfer
2021-04-22 9:12 ` Maciej W. Rozycki
2021-04-22 11:08 ` Thomas Bogendoerfer
2021-04-22 20:47 ` Maciej W. Rozycki
2021-04-27 12:16 ` Maciej W. Rozycki
2021-04-22 11:17 ` Andreas Schwab
2021-04-21 12:01 ` [PATCH 0/4] Reinstate and improve MIPS `do_div' implementation Thomas Bogendoerfer
2021-04-21 13:12 ` Maciej W. Rozycki
2021-04-21 16:00 ` H. Nikolaus Schaller
2021-04-21 19:04 ` Maciej W. Rozycki
2021-04-22 5:53 ` H. Nikolaus Schaller
2021-04-22 13:39 ` Jiaxun Yang
2021-04-22 15:58 ` Maciej W. Rozycki
2021-04-22 16:00 ` H. Nikolaus Schaller
2021-04-22 16:55 ` Maciej W. Rozycki
2021-04-22 17:06 ` H. Nikolaus Schaller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.21.2104200113290.44318@angie.orcam.me.uk \
--to=macro@orcam.me.uk \
--cc=arnd@arndb.de \
--cc=chenhuacai@kernel.org \
--cc=chenhuacai@loongson.cn \
--cc=jiaxun.yang@flygoat.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mips@vger.kernel.org \
--cc=tsbogend@alpha.franken.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).