+ numa-balancing-optimize-page-placement-for-memory-tiering-system.patch added to -mm tree

* + numa-balancing-optimize-page-placement-for-memory-tiering-system.patch added to -mm tree
@ 2022-02-01 22:20 Andrew Morton
  2022-02-02 10:19 ` Peter Zijlstra
  0 siblings, 1 reply; 4+ messages in thread
From: Andrew Morton @ 2022-02-01 22:20 UTC (permalink / raw)
  To: mm-commits, ziy, zhongjiang-ali, weixugc, shy828301, shakeelb,
	riel, peterz, osalvador, mhocko, mgorman, hasanalmaruf,
	feng.tang, dave.hansen, baolin.wang, ying.huang, akpm


The patch titled
     Subject: NUMA balancing: optimize page placement for memory tiering system
has been added to the -mm tree.  Its filename is
     numa-balancing-optimize-page-placement-for-memory-tiering-system.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/numa-balancing-optimize-page-placement-for-memory-tiering-system.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/numa-balancing-optimize-page-placement-for-memory-tiering-system.patch

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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Huang Ying <ying.huang@intel.com>
Subject: NUMA balancing: optimize page placement for memory tiering system

With the advent of various new memory types, some machines will have
multiple types of memory, e.g.  DRAM and PMEM (persistent memory).  The
memory subsystem of these machines can be called memory tiering system,
because the performance of the different types of memory are usually
different.

In such system, because of the memory accessing pattern changing etc, some
pages in the slow memory may become hot globally.  So in this patch, the
NUMA balancing mechanism is enhanced to optimize the page placement among
the different memory types according to hot/cold dynamically.

In a typical memory tiering system, there are CPUs, fast memory and slow
memory in each physical NUMA node.  The CPUs and the fast memory will be
put in one logical node (called fast memory node), while the slow memory
will be put in another (faked) logical node (called slow memory node). 
That is, the fast memory is regarded as local while the slow memory is
regarded as remote.  So it's possible for the recently accessed pages in
the slow memory node to be promoted to the fast memory node via the
existing NUMA balancing mechanism.

The original NUMA balancing mechanism will stop to migrate pages if the
free memory of the target node becomes below the high watermark.  This is
a reasonable policy if there's only one memory type.  But this makes the
original NUMA balancing mechanism almost do not work to optimize page
placement among different memory types.  Details are as follows.

It's the common cases that the working-set size of the workload is larger
than the size of the fast memory nodes.  Otherwise, it's unnecessary to
use the slow memory at all.  So, there are almost always no enough free
pages in the fast memory nodes, so that the globally hot pages in the slow
memory node cannot be promoted to the fast memory node.  To solve the
issue, we have 2 choices as follows,

a. Ignore the free pages watermark checking when promoting hot pages
   from the slow memory node to the fast memory node.  This will
   create some memory pressure in the fast memory node, thus trigger
   the memory reclaiming.  So that, the cold pages in the fast memory
   node will be demoted to the slow memory node.

b. Make kswapd of the fast memory node to reclaim pages until the
   free pages are a little (for example, high_watermark / 4) more than
   the high watermark.  Then, if the free pages of the fast memory
   node reaches high watermark, and some hot pages need to be
   promoted, kswapd of the fast memory node will be waken up to demote
   more cold pages in the fast memory node to the slow memory node.
   This will free some extra space in the fast memory node, so the hot
   pages in the slow memory node can be promoted to the fast memory
   node.

The choice "a" may create high memory pressure in the fast memory node. 
If the memory pressure of the workload is high, the memory pressure may
become so high that the memory allocation latency of the workload is
influenced, e.g.  the direct reclaiming may be triggered.

The choice "b" works much better at this aspect.  If the memory pressure
of the workload is high, the hot pages promotion will stop earlier because
its allocation watermark is higher than that of the normal memory
allocation.  So in this patch, choice "b" is implemented.

In addition to the original page placement optimization among sockets, the
NUMA balancing mechanism is extended to be used to optimize page placement
according to hot/cold among different memory types.  So the sysctl user
space interface (numa_balancing) is extended in a backward compatible way
as follow, so that the users can enable/disable these functionality
individually.

The sysctl is converted from a Boolean value to a bits field.  The
definition of the flags is,

- 0x0: NUMA_BALANCING_DISABLED
- 0x1: NUMA_BALANCING_NORMAL
- 0x2: NUMA_BALANCING_MEMORY_TIERING

We have tested the patch with the pmbench memory accessing benchmark with
the 80:20 read/write ratio and the Gauss access address distribution on a
2 socket Intel server with Optane DC Persistent Memory Model.  The test
results shows that the pmbench score can improve up to 95.9%.

Link: https://lkml.kernel.org/r/20220128082751.593478-3-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: zhongjiang-ali <zhongjiang-ali@linux.alibaba.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Hasan Al Maruf <hasanalmaruf@fb.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Documentation/admin-guide/sysctl/kernel.rst |   31 ++++++++++++------
 include/linux/sched/sysctl.h                |   10 +++++
 kernel/sched/core.c                         |   21 +++++++++---
 kernel/sysctl.c                             |    2 -
 mm/migrate.c                                |   19 +++++++++--
 mm/vmscan.c                                 |   17 +++++++++
 6 files changed, 83 insertions(+), 17 deletions(-)

--- a/Documentation/admin-guide/sysctl/kernel.rst~numa-balancing-optimize-page-placement-for-memory-tiering-system
+++ a/Documentation/admin-guide/sysctl/kernel.rst
@@ -595,16 +595,23 @@ Documentation/admin-guide/kernel-paramet
 numa_balancing
 ==============
 
-Enables/disables automatic page fault based NUMA memory
-balancing. Memory is moved automatically to nodes
-that access it often.
-
-Enables/disables automatic NUMA memory balancing. On NUMA machines, there
-is a performance penalty if remote memory is accessed by a CPU. When this
-feature is enabled the kernel samples what task thread is accessing memory
-by periodically unmapping pages and later trapping a page fault. At the
-time of the page fault, it is determined if the data being accessed should
-be migrated to a local memory node.
+Enables/disables and configure automatic page fault based NUMA memory
+balancing.  Memory is moved automatically to nodes that access it
+often.  The value to set can be the result to OR the following,
+
+= =================================
+0x0 NUMA_BALANCING_DISABLED
+0x1 NUMA_BALANCING_NORMAL
+0x2 NUMA_BALANCING_MEMORY_TIERING
+= =================================
+
+Or NUMA_BALANCING_NORMAL to optimize page placement among different
+NUMA nodes to reduce remote accessing.  On NUMA machines, there is a
+performance penalty if remote memory is accessed by a CPU. When this
+feature is enabled the kernel samples what task thread is accessing
+memory by periodically unmapping pages and later trapping a page
+fault. At the time of the page fault, it is determined if the data
+being accessed should be migrated to a local memory node.
 
 The unmapping of pages and trapping faults incur additional overhead that
 ideally is offset by improved memory locality but there is no universal
@@ -615,6 +622,10 @@ faults may be controlled by the `numa_ba
 numa_balancing_scan_delay_ms, numa_balancing_scan_period_max_ms,
 numa_balancing_scan_size_mb`_, and numa_balancing_settle_count sysctls.
 
+Or NUMA_BALANCING_MEMORY_TIERING to optimize page placement among
+different types of memory (represented as different NUMA nodes) to
+place the hot pages in the fast memory.  This is implemented based on
+unmapping and page fault too.
 
 numa_balancing_scan_period_min_ms, numa_balancing_scan_delay_ms, numa_balancing_scan_period_max_ms, numa_balancing_scan_size_mb
 ===============================================================================================================================
--- a/include/linux/sched/sysctl.h~numa-balancing-optimize-page-placement-for-memory-tiering-system
+++ a/include/linux/sched/sysctl.h
@@ -23,6 +23,16 @@ enum sched_tunable_scaling {
 	SCHED_TUNABLESCALING_END,
 };
 
+#define NUMA_BALANCING_DISABLED		0x0
+#define NUMA_BALANCING_NORMAL		0x1
+#define NUMA_BALANCING_MEMORY_TIERING	0x2
+
+#ifdef CONFIG_NUMA_BALANCING
+extern int sysctl_numa_balancing_mode;
+#else
+#define sysctl_numa_balancing_mode	0
+#endif
+
 /*
  *  control realtime throttling:
  *
--- a/kernel/sched/core.c~numa-balancing-optimize-page-placement-for-memory-tiering-system
+++ a/kernel/sched/core.c
@@ -4279,7 +4279,9 @@ DEFINE_STATIC_KEY_FALSE(sched_numa_balan
 
 #ifdef CONFIG_NUMA_BALANCING
 
-void set_numabalancing_state(bool enabled)
+int sysctl_numa_balancing_mode;
+
+static void __set_numabalancing_state(bool enabled)
 {
 	if (enabled)
 		static_branch_enable(&sched_numa_balancing);
@@ -4287,13 +4289,22 @@ void set_numabalancing_state(bool enable
 		static_branch_disable(&sched_numa_balancing);
 }
 
+void set_numabalancing_state(bool enabled)
+{
+	if (enabled)
+		sysctl_numa_balancing_mode = NUMA_BALANCING_NORMAL;
+	else
+		sysctl_numa_balancing_mode = NUMA_BALANCING_DISABLED;
+	__set_numabalancing_state(enabled);
+}
+
 #ifdef CONFIG_PROC_SYSCTL
 int sysctl_numa_balancing(struct ctl_table *table, int write,
 			  void *buffer, size_t *lenp, loff_t *ppos)
 {
 	struct ctl_table t;
 	int err;
-	int state = static_branch_likely(&sched_numa_balancing);
+	int state = sysctl_numa_balancing_mode;
 
 	if (write && !capable(CAP_SYS_ADMIN))
 		return -EPERM;
@@ -4303,8 +4314,10 @@ int sysctl_numa_balancing(struct ctl_tab
 	err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
 	if (err < 0)
 		return err;
-	if (write)
-		set_numabalancing_state(state);
+	if (write) {
+		sysctl_numa_balancing_mode = state;
+		__set_numabalancing_state(state);
+	}
 	return err;
 }
 #endif
--- a/kernel/sysctl.c~numa-balancing-optimize-page-placement-for-memory-tiering-system
+++ a/kernel/sysctl.c
@@ -1687,7 +1687,7 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= sysctl_numa_balancing,
 		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_ONE,
+		.extra2		= SYSCTL_FOUR,
 	},
 #endif /* CONFIG_NUMA_BALANCING */
 	{
--- a/mm/migrate.c~numa-balancing-optimize-page-placement-for-memory-tiering-system
+++ a/mm/migrate.c
@@ -51,6 +51,7 @@
 #include <linux/oom.h>
 #include <linux/memory.h>
 #include <linux/random.h>
+#include <linux/sched/sysctl.h>
 
 #include <asm/tlbflush.h>
 
@@ -2035,16 +2036,30 @@ static int numamigrate_isolate_page(pg_d
 {
 	int page_lru;
 	int nr_pages = thp_nr_pages(page);
+	int order = compound_order(page);
 
-	VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
+	VM_BUG_ON_PAGE(order && !PageTransHuge(page), page);
 
 	/* Do not migrate THP mapped by multiple processes */
 	if (PageTransHuge(page) && total_mapcount(page) > 1)
 		return 0;
 
 	/* Avoid migrating to a node that is nearly full */
-	if (!migrate_balanced_pgdat(pgdat, nr_pages))
+	if (!migrate_balanced_pgdat(pgdat, nr_pages)) {
+		int z;
+
+		if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) ||
+		    !numa_demotion_enabled)
+			return 0;
+		if (next_demotion_node(pgdat->node_id) == NUMA_NO_NODE)
+			return 0;
+		for (z = pgdat->nr_zones - 1; z >= 0; z--) {
+			if (populated_zone(pgdat->node_zones + z))
+				break;
+		}
+		wakeup_kswapd(pgdat->node_zones + z, 0, order, ZONE_MOVABLE);
 		return 0;
+	}
 
 	if (isolate_lru_page(page))
 		return 0;
--- a/mm/vmscan.c~numa-balancing-optimize-page-placement-for-memory-tiering-system
+++ a/mm/vmscan.c
@@ -56,6 +56,7 @@
 
 #include <linux/swapops.h>
 #include <linux/balloon_compaction.h>
+#include <linux/sched/sysctl.h>
 
 #include "internal.h"
 
@@ -3939,6 +3940,13 @@ static bool pgdat_watermark_boosted(pg_d
 }
 
 /*
+ * Keep the free pages on fast memory node a little more than the high
+ * watermark to accommodate the promoted pages.
+ */
+#define NUMA_BALANCING_PROMOTE_WATERMARK_DIV	4
+#define NUMA_BALANCING_PROMOTE_WATERMARK_MIN	(10UL * 1024 * 1024 >> PAGE_SHIFT)
+
+/*
  * Returns true if there is an eligible zone balanced for the request order
  * and highest_zoneidx
  */
@@ -3959,6 +3967,15 @@ static bool pgdat_balanced(pg_data_t *pg
 			continue;
 
 		mark = high_wmark_pages(zone);
+		if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
+		    numa_demotion_enabled &&
+		    next_demotion_node(pgdat->node_id) != NUMA_NO_NODE) {
+			unsigned long promote_mark;
+
+			promote_mark = max(NUMA_BALANCING_PROMOTE_WATERMARK_MIN,
+				mark / NUMA_BALANCING_PROMOTE_WATERMARK_DIV);
+			mark += promote_mark;
+		}
 		if (zone_watermark_ok_safe(zone, order, mark, highest_zoneidx))
 			return true;
 	}
_

Patches currently in -mm which might be from ying.huang@intel.com are

numa-balancing-add-page-promotion-counter.patch
numa-balancing-optimize-page-placement-for-memory-tiering-system.patch
memory-tiering-skip-to-scan-fast-memory.patch


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