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From: Mel Gorman <mgorman@suse.de>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>, Rik van Riel <riel@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
	Ingo Molnar <mingo@kernel.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Linux-MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>, Mel Gorman <mgorman@suse.de>
Subject: [PATCH 22/63] sched: Favour moving tasks towards the preferred node
Date: Mon,  7 Oct 2013 11:29:00 +0100
Message-ID: <1381141781-10992-23-git-send-email-mgorman@suse.de> (raw)
In-Reply-To: <1381141781-10992-1-git-send-email-mgorman@suse.de>

This patch favours moving tasks towards NUMA node that recorded a higher
number of NUMA faults during active load balancing.  Ideally this is
self-reinforcing as the longer the task runs on that node, the more faults
it should incur causing task_numa_placement to keep the task running on that
node. In reality a big weakness is that the nodes CPUs can be overloaded
and it would be more efficient to queue tasks on an idle node and migrate
to the new node. This would require additional smarts in the balancer so
for now the balancer will simply prefer to place the task on the preferred
node for a PTE scans which is controlled by the numa_balancing_settle_count
sysctl. Once the settle_count number of scans has complete the schedule
is free to place the task on an alternative node if the load is imbalanced.

[srikar@linux.vnet.ibm.com: Fixed statistics]
[peterz@infradead.org: Tunable and use higher faults instead of preferred]
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 Documentation/sysctl/kernel.txt |  8 +++++-
 include/linux/sched.h           |  1 +
 kernel/sched/core.c             |  3 +-
 kernel/sched/fair.c             | 63 ++++++++++++++++++++++++++++++++++++++---
 kernel/sched/features.h         |  7 +++++
 kernel/sysctl.c                 |  7 +++++
 6 files changed, 83 insertions(+), 6 deletions(-)

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 8cd7e5f..d48bca4 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -375,7 +375,8 @@ feature should be disabled. Otherwise, if the system overhead from the
 feature is too high then the rate the kernel samples for NUMA hinting
 faults may be controlled by the numa_balancing_scan_period_min_ms,
 numa_balancing_scan_delay_ms, numa_balancing_scan_period_reset,
-numa_balancing_scan_period_max_ms and numa_balancing_scan_size_mb sysctls.
+numa_balancing_scan_period_max_ms, numa_balancing_scan_size_mb and
+numa_balancing_settle_count sysctls.
 
 ==============================================================
 
@@ -420,6 +421,11 @@ scanned for a given scan.
 numa_balancing_scan_period_reset is a blunt instrument that controls how
 often a tasks scan delay is reset to detect sudden changes in task behaviour.
 
+numa_balancing_settle_count is how many scan periods must complete before
+the schedule balancer stops pushing the task towards a preferred node. This
+gives the scheduler a chance to place the task on an alternative node if the
+preferred node is overloaded.
+
 ==============================================================
 
 osrelease, ostype & version:
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2e02757..d5ae4bd 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -768,6 +768,7 @@ enum cpu_idle_type {
 #define SD_ASYM_PACKING		0x0800  /* Place busy groups earlier in the domain */
 #define SD_PREFER_SIBLING	0x1000	/* Prefer to place tasks in a sibling domain */
 #define SD_OVERLAP		0x2000	/* sched_domains of this level overlap */
+#define SD_NUMA			0x4000	/* cross-node balancing */
 
 extern int __weak arch_sd_sibiling_asym_packing(void);
 
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 201c953..3515c41 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1626,7 +1626,7 @@ static void __sched_fork(struct task_struct *p)
 
 	p->node_stamp = 0ULL;
 	p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0;
-	p->numa_migrate_seq = p->mm ? p->mm->numa_scan_seq - 1 : 0;
+	p->numa_migrate_seq = 0;
 	p->numa_scan_period = sysctl_numa_balancing_scan_delay;
 	p->numa_preferred_nid = -1;
 	p->numa_work.next = &p->numa_work;
@@ -5661,6 +5661,7 @@ sd_numa_init(struct sched_domain_topology_level *tl, int cpu)
 					| 0*SD_SHARE_PKG_RESOURCES
 					| 1*SD_SERIALIZE
 					| 0*SD_PREFER_SIBLING
+					| 1*SD_NUMA
 					| sd_local_flags(level)
 					,
 		.last_balance		= jiffies,
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6227fb4..8c2b779 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -877,6 +877,15 @@ static unsigned int task_scan_max(struct task_struct *p)
 	return max(smin, smax);
 }
 
+/*
+ * Once a preferred node is selected the scheduler balancer will prefer moving
+ * a task to that node for sysctl_numa_balancing_settle_count number of PTE
+ * scans. This will give the process the chance to accumulate more faults on
+ * the preferred node but still allow the scheduler to move the task again if
+ * the nodes CPUs are overloaded.
+ */
+unsigned int sysctl_numa_balancing_settle_count __read_mostly = 3;
+
 static void task_numa_placement(struct task_struct *p)
 {
 	int seq, nid, max_nid = -1;
@@ -888,6 +897,7 @@ static void task_numa_placement(struct task_struct *p)
 	if (p->numa_scan_seq == seq)
 		return;
 	p->numa_scan_seq = seq;
+	p->numa_migrate_seq++;
 	p->numa_scan_period_max = task_scan_max(p);
 
 	/* Find the node with the highest number of faults */
@@ -907,8 +917,10 @@ static void task_numa_placement(struct task_struct *p)
 	}
 
 	/* Update the tasks preferred node if necessary */
-	if (max_faults && max_nid != p->numa_preferred_nid)
+	if (max_faults && max_nid != p->numa_preferred_nid) {
 		p->numa_preferred_nid = max_nid;
+		p->numa_migrate_seq = 0;
+	}
 }
 
 /*
@@ -4070,6 +4082,38 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
 	return delta < (s64)sysctl_sched_migration_cost;
 }
 
+#ifdef CONFIG_NUMA_BALANCING
+/* Returns true if the destination node has incurred more faults */
+static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
+{
+	int src_nid, dst_nid;
+
+	if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults ||
+	    !(env->sd->flags & SD_NUMA)) {
+		return false;
+	}
+
+	src_nid = cpu_to_node(env->src_cpu);
+	dst_nid = cpu_to_node(env->dst_cpu);
+
+	if (src_nid == dst_nid ||
+	    p->numa_migrate_seq >= sysctl_numa_balancing_settle_count)
+		return false;
+
+	if (dst_nid == p->numa_preferred_nid ||
+	    p->numa_faults[dst_nid] > p->numa_faults[src_nid])
+		return true;
+
+	return false;
+}
+#else
+static inline bool migrate_improves_locality(struct task_struct *p,
+					     struct lb_env *env)
+{
+	return false;
+}
+#endif
+
 /*
  * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
  */
@@ -4125,11 +4169,22 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env)
 
 	/*
 	 * Aggressive migration if:
-	 * 1) task is cache cold, or
-	 * 2) too many balance attempts have failed.
+	 * 1) destination numa is preferred
+	 * 2) task is cache cold, or
+	 * 3) too many balance attempts have failed.
 	 */
-
 	tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);
+
+	if (migrate_improves_locality(p, env)) {
+#ifdef CONFIG_SCHEDSTATS
+		if (tsk_cache_hot) {
+			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
+			schedstat_inc(p, se.statistics.nr_forced_migrations);
+		}
+#endif
+		return 1;
+	}
+
 	if (!tsk_cache_hot ||
 		env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
 
diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index cba5c61..d9278ce 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -67,4 +67,11 @@ SCHED_FEAT(LB_MIN, false)
  */
 #ifdef CONFIG_NUMA_BALANCING
 SCHED_FEAT(NUMA,	false)
+
+/*
+ * NUMA_FAVOUR_HIGHER will favor moving tasks towards nodes where a
+ * higher number of hinting faults are recorded during active load
+ * balancing.
+ */
+SCHED_FEAT(NUMA_FAVOUR_HIGHER, true)
 #endif
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index b2f06f3..42f616a 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -391,6 +391,13 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
+	{
+		.procname       = "numa_balancing_settle_count",
+		.data           = &sysctl_numa_balancing_settle_count,
+		.maxlen         = sizeof(unsigned int),
+		.mode           = 0644,
+		.proc_handler   = proc_dointvec,
+	},
 #endif /* CONFIG_NUMA_BALANCING */
 #endif /* CONFIG_SCHED_DEBUG */
 	{
-- 
1.8.4

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  parent reply index

Thread overview: 136+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-10-07 10:28 [PATCH 0/63] Basic scheduler support for automatic NUMA balancing V9 Mel Gorman
2013-10-07 10:28 ` [PATCH 01/63] hotplug: Optimize {get,put}_online_cpus() Mel Gorman
2013-10-07 10:28 ` [PATCH 02/63] mm: numa: Document automatic NUMA balancing sysctls Mel Gorman
2013-10-07 12:46   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 03/63] sched, numa: Comment fixlets Mel Gorman
2013-10-07 12:46   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 04/63] mm: numa: Do not account for a hinting fault if we raced Mel Gorman
2013-10-07 12:47   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 05/63] mm: Wait for THP migrations to complete during NUMA hinting faults Mel Gorman
2013-10-07 13:55   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 06/63] mm: Prevent parallel splits during THP migration Mel Gorman
2013-10-07 14:01   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 07/63] mm: numa: Sanitize task_numa_fault() callsites Mel Gorman
2013-10-07 14:02   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 08/63] mm: Close races between THP migration and PMD numa clearing Mel Gorman
2013-10-07 14:02   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 09/63] mm: Account for a THP NUMA hinting update as one PTE update Mel Gorman
2013-10-07 14:02   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 10/63] mm: Do not flush TLB during protection change if !pte_present && !migration_entry Mel Gorman
2013-10-07 15:12   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 11/63] mm: Only flush TLBs if a transhuge PMD is modified for NUMA pte scanning Mel Gorman
2013-10-07 10:28 ` [PATCH 12/63] mm: numa: Do not migrate or account for hinting faults on the zero page Mel Gorman
2013-10-07 17:10   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 13/63] sched: numa: Mitigate chance that same task always updates PTEs Mel Gorman
2013-10-07 17:24   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 14/63] sched: numa: Continue PTE scanning even if migrate rate limited Mel Gorman
2013-10-07 17:24   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 15/63] Revert "mm: sched: numa: Delay PTE scanning until a task is scheduled on a new node" Mel Gorman
2013-10-07 17:42   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 16/63] sched: numa: Initialise numa_next_scan properly Mel Gorman
2013-10-07 17:44   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 17/63] sched: Set the scan rate proportional to the memory usage of the task being scanned Mel Gorman
2013-10-07 17:44   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 18/63] sched: numa: Slow scan rate if no NUMA hinting faults are being recorded Mel Gorman
2013-10-07 18:02   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 19/63] sched: Track NUMA hinting faults on per-node basis Mel Gorman
2013-10-07 18:02   ` Rik van Riel
2013-12-04  5:32   ` Wanpeng Li
2013-12-04  5:37     ` Wanpeng Li
2013-10-07 10:28 ` [PATCH 20/63] sched: Select a preferred node with the most numa hinting faults Mel Gorman
2013-10-07 18:04   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 21/63] sched: Update NUMA hinting faults once per scan Mel Gorman
2013-10-07 18:39   ` Rik van Riel
2013-10-07 10:29 ` Mel Gorman [this message]
2013-10-07 18:39   ` [PATCH 22/63] sched: Favour moving tasks towards the preferred node Rik van Riel
2013-10-07 10:29 ` [PATCH 23/63] sched: Resist moving tasks towards nodes with fewer hinting faults Mel Gorman
2013-10-07 18:40   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 24/63] sched: Reschedule task on preferred NUMA node once selected Mel Gorman
2013-10-07 18:40   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 25/63] sched: Add infrastructure for split shared/private accounting of NUMA hinting faults Mel Gorman
2013-10-07 18:41   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 26/63] sched: Check current->mm before allocating NUMA faults Mel Gorman
2013-10-07 18:41   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 27/63] mm: numa: Scan pages with elevated page_mapcount Mel Gorman
2013-10-07 18:43   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 28/63] sched: Remove check that skips small VMAs Mel Gorman
2013-10-07 18:44   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 29/63] sched: Set preferred NUMA node based on number of private faults Mel Gorman
2013-10-07 18:45   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 30/63] sched: Do not migrate memory immediately after switching node Mel Gorman
2013-10-07 10:29 ` [PATCH 31/63] mm: numa: only unmap migrate-on-fault VMAs Mel Gorman
2013-10-07 10:29 ` [PATCH 32/63] sched: Avoid overloading CPUs on a preferred NUMA node Mel Gorman
2013-10-07 18:58   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 33/63] sched: Retry migration of tasks to CPU on a preferred node Mel Gorman
2013-10-07 18:58   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 34/63] sched: numa: increment numa_migrate_seq when task runs in correct location Mel Gorman
2013-10-07 10:29 ` [PATCH 35/63] sched: numa: Do not trap hinting faults for shared libraries Mel Gorman
2013-10-07 19:04   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 36/63] mm: numa: Only trap pmd hinting faults if we would otherwise trap PTE faults Mel Gorman
2013-10-07 19:06   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 37/63] stop_machine: Introduce stop_two_cpus() Mel Gorman
2013-10-07 10:29 ` [PATCH 38/63] sched: Introduce migrate_swap() Mel Gorman
2013-10-07 19:06   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 39/63] sched: numa: Use a system-wide search to find swap/migration candidates Mel Gorman
2013-10-07 19:07   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 40/63] sched: numa: Favor placing a task on the preferred node Mel Gorman
2013-10-07 19:07   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 41/63] sched: numa: fix placement of workloads spread across multiple nodes Mel Gorman
2013-10-07 10:29 ` [PATCH 42/63] mm: numa: Change page last {nid,pid} into {cpu,pid} Mel Gorman
2013-10-07 19:08   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 43/63] sched: numa: Use {cpu, pid} to create task groups for shared faults Mel Gorman
2013-10-07 19:09   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 44/63] sched: numa: Report a NUMA task group ID Mel Gorman
2013-10-07 19:09   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 45/63] mm: numa: copy cpupid on page migration Mel Gorman
2013-10-07 10:29 ` [PATCH 46/63] mm: numa: Do not group on RO pages Mel Gorman
2013-10-07 19:10   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 47/63] mm: numa: Do not batch handle PMD pages Mel Gorman
2013-10-07 19:11   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 48/63] sched: numa: stay on the same node if CLONE_VM Mel Gorman
2013-10-07 10:29 ` [PATCH 49/63] sched: numa: use group fault statistics in numa placement Mel Gorman
2013-10-07 10:29 ` [PATCH 50/63] sched: numa: call task_numa_free from do_execve Mel Gorman
2013-10-07 10:29 ` [PATCH 51/63] sched: numa: Prevent parallel updates to group stats during placement Mel Gorman
2013-10-07 19:13   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 52/63] sched: numa: add debugging Mel Gorman
2013-10-07 19:13   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 53/63] sched: numa: Decide whether to favour task or group weights based on swap candidate relationships Mel Gorman
2013-10-07 10:29 ` [PATCH 54/63] sched: numa: fix task or group comparison Mel Gorman
2013-10-07 10:29 ` [PATCH 55/63] sched: numa: Avoid migrating tasks that are placed on their preferred node Mel Gorman
2013-10-07 19:14   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 56/63] sched: numa: be more careful about joining numa groups Mel Gorman
2013-10-07 10:29 ` [PATCH 57/63] sched: numa: Take false sharing into account when adapting scan rate Mel Gorman
2013-10-07 19:14   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 58/63] sched: numa: adjust scan rate in task_numa_placement Mel Gorman
2013-10-07 10:29 ` [PATCH 59/63] sched: numa: Remove the numa_balancing_scan_period_reset sysctl Mel Gorman
2013-10-07 19:14   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 60/63] mm: numa: revert temporarily disabling of NUMA migration Mel Gorman
2013-10-07 10:29 ` [PATCH 61/63] sched: numa: skip some page migrations after a shared fault Mel Gorman
2013-10-07 10:29 ` [PATCH 62/63] sched: numa: use unsigned longs for numa group fault stats Mel Gorman
2013-10-07 19:15   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 63/63] sched: numa: periodically retry task_numa_migrate Mel Gorman
2013-10-09 11:03 ` [PATCH 0/63] Basic scheduler support for automatic NUMA balancing V9 Ingo Molnar
2013-10-09 11:11   ` Ingo Molnar
2013-10-09 11:13     ` Ingo Molnar
2013-10-09 12:05   ` Peter Zijlstra
2013-10-09 12:48     ` Ingo Molnar
2013-10-10  7:05   ` Mel Gorman
2013-10-09 16:28 ` Ingo Molnar
2013-10-09 16:29   ` Ingo Molnar
2013-10-09 16:57     ` Ingo Molnar
2013-10-09 17:09       ` Ingo Molnar
2013-10-09 17:11         ` Peter Zijlstra
2013-10-09 17:08   ` Peter Zijlstra
2013-10-09 17:15     ` Ingo Molnar
2013-10-09 17:18       ` Peter Zijlstra
2013-10-24 12:26 ` Automatic NUMA balancing patches for tip-urgent/stable Mel Gorman
2013-10-26 12:11   ` Ingo Molnar
2013-10-29  9:42     ` Mel Gorman
2013-10-29  9:48       ` Ingo Molnar
2013-10-29 10:24         ` Mel Gorman
2013-10-29 10:41           ` Ingo Molnar
2013-10-29 12:48             ` Mel Gorman
2013-10-31  9:51   ` [RFC GIT PULL] NUMA-balancing memory corruption fixes Ingo Molnar
2013-10-31 22:25     ` Linus Torvalds
2013-11-01  7:36       ` Ingo Molnar
  -- strict thread matches above, loose matches on Subject: below --
2013-09-27 13:26 [PATCH 0/63] Basic scheduler support for automatic NUMA balancing V8 Mel Gorman
2013-09-27 13:27 ` [PATCH 22/63] sched: Favour moving tasks towards the preferred node Mel Gorman

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