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 06/27] sched, numa: Mitigate chance that same task always updates PTEs
Date: Thu, 8 Aug 2013 15:00:18 +0100 [thread overview]
Message-ID: <1375970439-5111-7-git-send-email-mgorman@suse.de> (raw)
In-Reply-To: <1375970439-5111-1-git-send-email-mgorman@suse.de>
From: Peter Zijlstra <peterz@infradead.org>
With a trace_printk("working\n"); right after the cmpxchg in
task_numa_work() we can see that of a 4 thread process, its always the
same task winning the race and doing the protection change.
This is a problem since the task doing the protection change has a
penalty for taking faults -- it is busy when marking the PTEs. If its
always the same task the ->numa_faults[] get severely skewed.
Avoid this by delaying the task doing the protection change such that
it is unlikely to win the privilege again.
Before:
root@interlagos:~# grep "thread 0/.*working" /debug/tracing/trace | tail -15
thread 0/0-3232 [022] .... 212.787402: task_numa_work: working
thread 0/0-3232 [022] .... 212.888473: task_numa_work: working
thread 0/0-3232 [022] .... 212.989538: task_numa_work: working
thread 0/0-3232 [022] .... 213.090602: task_numa_work: working
thread 0/0-3232 [022] .... 213.191667: task_numa_work: working
thread 0/0-3232 [022] .... 213.292734: task_numa_work: working
thread 0/0-3232 [022] .... 213.393804: task_numa_work: working
thread 0/0-3232 [022] .... 213.494869: task_numa_work: working
thread 0/0-3232 [022] .... 213.596937: task_numa_work: working
thread 0/0-3232 [022] .... 213.699000: task_numa_work: working
thread 0/0-3232 [022] .... 213.801067: task_numa_work: working
thread 0/0-3232 [022] .... 213.903155: task_numa_work: working
thread 0/0-3232 [022] .... 214.005201: task_numa_work: working
thread 0/0-3232 [022] .... 214.107266: task_numa_work: working
thread 0/0-3232 [022] .... 214.209342: task_numa_work: working
After:
root@interlagos:~# grep "thread 0/.*working" /debug/tracing/trace | tail -15
thread 0/0-3253 [005] .... 136.865051: task_numa_work: working
thread 0/2-3255 [026] .... 136.965134: task_numa_work: working
thread 0/3-3256 [024] .... 137.065217: task_numa_work: working
thread 0/3-3256 [024] .... 137.165302: task_numa_work: working
thread 0/3-3256 [024] .... 137.265382: task_numa_work: working
thread 0/0-3253 [004] .... 137.366465: task_numa_work: working
thread 0/2-3255 [026] .... 137.466549: task_numa_work: working
thread 0/0-3253 [004] .... 137.566629: task_numa_work: working
thread 0/0-3253 [004] .... 137.666711: task_numa_work: working
thread 0/1-3254 [028] .... 137.766799: task_numa_work: working
thread 0/0-3253 [004] .... 137.866876: task_numa_work: working
thread 0/2-3255 [026] .... 137.966960: task_numa_work: working
thread 0/1-3254 [028] .... 138.067041: task_numa_work: working
thread 0/2-3255 [026] .... 138.167123: task_numa_work: working
thread 0/3-3256 [024] .... 138.267207: task_numa_work: working
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
kernel/sched/fair.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 679cfcf..2a08727 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -946,6 +946,12 @@ void task_numa_work(struct callback_head *work)
return;
/*
+ * Delay this task enough that another task of this mm will likely win
+ * the next time around.
+ */
+ p->node_stamp += 2 * TICK_NSEC;
+
+ /*
* Do not set pte_numa if the current running node is rate-limited.
* This loses statistics on the fault but if we are unwilling to
* migrate to this node, it is less likely we can do useful work
@@ -1026,7 +1032,7 @@ void task_tick_numa(struct rq *rq, struct task_struct *curr)
if (now - curr->node_stamp > period) {
if (!curr->node_stamp)
curr->numa_scan_period = sysctl_numa_balancing_scan_period_min;
- curr->node_stamp = now;
+ curr->node_stamp += period;
if (!time_before(jiffies, curr->mm->numa_next_scan)) {
init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
--
1.8.1.4
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2013-08-08 14:00 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-08 14:00 [PATCH 0/27] Basic scheduler support for automatic NUMA balancing V6 Mel Gorman
2013-08-08 14:00 ` [PATCH 01/27] mm: numa: Document automatic NUMA balancing sysctls Mel Gorman
2013-08-08 14:00 ` [PATCH 02/27] sched, numa: Comment fixlets Mel Gorman
2013-08-08 14:00 ` [PATCH 03/27] mm: numa: Account for THP numa hinting faults on the correct node Mel Gorman
2013-08-08 14:00 ` [PATCH 04/27] mm: numa: Do not migrate or account for hinting faults on the zero page Mel Gorman
2013-08-08 14:00 ` [PATCH 05/27] mm, numa: Sanitize task_numa_fault() callsites Mel Gorman
2013-08-08 14:00 ` Mel Gorman [this message]
2013-08-08 14:00 ` [PATCH 07/27] sched, numa: Continue PTE scanning even if migrate rate limited Mel Gorman
2013-08-08 14:00 ` [PATCH 08/27] Revert "mm: sched: numa: Delay PTE scanning until a task is scheduled on a new node" Mel Gorman
2013-08-08 14:00 ` [PATCH 09/27] sched: numa: Initialise numa_next_scan properly Mel Gorman
2013-08-08 14:00 ` [PATCH 10/27] sched: numa: Slow scan rate if no NUMA hinting faults are being recorded Mel Gorman
2013-08-08 14:00 ` [PATCH 11/27] sched: Set the scan rate proportional to the memory usage of the task being scanned Mel Gorman
2013-08-08 14:00 ` [PATCH 12/27] sched: numa: Correct adjustment of numa_scan_period Mel Gorman
2013-08-08 14:00 ` [PATCH 13/27] mm: Only flush TLBs if a transhuge PMD is modified for NUMA pte scanning Mel Gorman
2013-08-08 14:00 ` [PATCH 14/27] mm: Do not flush TLB during protection change if !pte_present && !migration_entry Mel Gorman
2013-08-08 14:00 ` [PATCH 15/27] sched: Track NUMA hinting faults on per-node basis Mel Gorman
2013-08-08 14:00 ` [PATCH 16/27] sched: Select a preferred node with the most numa hinting faults Mel Gorman
2013-08-08 14:00 ` [PATCH 17/27] sched: Update NUMA hinting faults once per scan Mel Gorman
2013-08-08 14:00 ` [PATCH 18/27] sched: Favour moving tasks towards the preferred node Mel Gorman
2013-08-08 14:00 ` [PATCH 19/27] sched: Resist moving tasks towards nodes with fewer hinting faults Mel Gorman
2013-08-08 14:00 ` [PATCH 20/27] sched: Reschedule task on preferred NUMA node once selected Mel Gorman
2013-08-08 14:00 ` [PATCH 21/27] sched: Add infrastructure for split shared/private accounting of NUMA hinting faults Mel Gorman
2013-08-08 14:00 ` [PATCH 22/27] sched: Check current->mm before allocating NUMA faults Mel Gorman
2013-08-08 14:00 ` [PATCH 23/27] mm: numa: Scan pages with elevated page_mapcount Mel Gorman
2013-08-08 14:00 ` [PATCH 24/27] sched: Remove check that skips small VMAs Mel Gorman
2013-08-08 14:00 ` [PATCH 25/27] sched: Set preferred NUMA node based on number of private faults Mel Gorman
2013-08-08 14:00 ` [PATCH 26/27] sched: Avoid overloading CPUs on a preferred NUMA node Mel Gorman
2013-08-08 14:00 ` [PATCH 27/27] sched: Retry migration of tasks to CPU on a preferred node Mel Gorman
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=1375970439-5111-7-git-send-email-mgorman@suse.de \
--to=mgorman@suse.de \
--cc=a.p.zijlstra@chello.nl \
--cc=aarcange@redhat.com \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mingo@kernel.org \
--cc=riel@redhat.com \
--cc=srikar@linux.vnet.ibm.com \
/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).