From: Mel Gorman <mgorman@suse.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: 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>
Subject: Re: [PATCH 5/8] sched: Favour moving tasks towards the preferred node
Date: Fri, 28 Jun 2013 14:45:35 +0100 [thread overview]
Message-ID: <20130628134535.GX1875@suse.de> (raw)
In-Reply-To: <20130627161127.GZ28407@twins.programming.kicks-ass.net>
On Thu, Jun 27, 2013 at 06:11:27PM +0200, Peter Zijlstra wrote:
> On Wed, Jun 26, 2013 at 03:38:04PM +0100, Mel Gorman wrote:
> > +/* 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 (!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)
> > + return false;
> > +
> > + if (p->numa_migrate_seq < sysctl_numa_balancing_settle_count &&
> > + p->numa_preferred_nid == dst_nid)
> > + return true;
> > +
> > + return false;
> > +}
>
> Also, until I just actually _read_ that function; I assumed it would
> compare p->numa_faults[src_nid] and p->numa_faults[dst_nid]. Because
> even when the dst_nid isn't the preferred nid; it might still have more
> pages than where we currently are.
>
I tested something like this and also tested it when only taking shared
accesses into account but it performed badly in some cases. I've included
the last patch I tested below for reference but dropped it until I figured
out why it performed badly. I guessed it was due to increased bouncing
due to shared faults but didn't prove it.
> Idem with the proposed migrate_degrades_locality().
>
> Something like so I suppose
>
> ---
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3969,6 +3969,7 @@ task_hot(struct task_struct *p, u64 now,
> 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)
> {
> @@ -3983,13 +3984,50 @@ static bool migrate_improves_locality(st
> if (src_nid == dst_nid)
> return false;
>
> - if (p->numa_migrate_seq < sysctl_numa_balancing_settle_count &&
> - p->numa_preferred_nid == dst_nid)
> + if (p->numa_migrate_seq >= sysctl_numa_balancing_settle_count)
> + return false;
> +
> + if (p->numa_preferred_nid == dst_nid)
> + return true;
> +
> + if (p->numa_faults[src_nid] < p->numa_faults[dst_nid])
> + return true;
> +
> + return false;
> +}
> +
I tested something like this.
> +static vool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
> +{
> + int src_nid, dst_nid;
> +
> + if (!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)
> + return false;
> +
> + if (p->numa_faults[src_nid] > p->numa_faults[dst_nid])
> return true;
>
> return false;
> }
But I had not tried this and it makes sense. I'll test it out and include
it in the next revision if it looks good. Unless you object I'll add
your signed-off because the version of the patch I'm about to test looks
almost identical to this.
>
> +#else
> +
> +static inline bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
> +{
> + return false;
> +}
> +
> +static inline bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
> +{
> + return false;
> +}
> +
> +#endif /* CONFIG_NUMA_BALANCING */
>
> /*
> * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
> @@ -4055,8 +4093,10 @@ int can_migrate_task(struct task_struct
> return 1;
>
> tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);
> + if (!tsk_cache_hot)
> + tsk_cache_hot = migrate_degrades_locality(p, env);
> if (!tsk_cache_hot ||
> - env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
> + env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
>
> if (tsk_cache_hot) {
> schedstat_inc(env->sd, lb_hot_gained[env->idle]);
>
This is the last patch similar to this idea I tested.
---8<---
sched: Favour moving tasks towards nodes that incurred more faults
Signed-off-by: Mel Gorman <mgorman@suse.de>
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e9bbb70..3379ca4 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3980,9 +3980,18 @@ static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
if (src_nid == dst_nid)
return false;
- if (p->numa_migrate_seq < sysctl_numa_balancing_settle_count &&
- p->numa_preferred_nid == dst_nid)
- return true;
+ if (p->numa_migrate_seq < sysctl_numa_balancing_settle_count) {
+ if (p->numa_preferred_nid == dst_nid)
+ return true;
+
+ /*
+ * Move towards node if there were a higher number of shared
+ * NUMA hinting faults
+ */
+ if (p->numa_faults[task_faults_idx(dst_nid, 0)] >
+ p->numa_faults[task_faults_idx(src_nid, 0)])
+ return true;
+ }
return false;
}
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2013-06-28 13:45 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-26 14:37 [PATCH 0/6] Basic scheduler support for automatic NUMA balancing Mel Gorman
2013-06-26 14:38 ` [PATCH 1/8] mm: numa: Document automatic NUMA balancing sysctls Mel Gorman
2013-06-26 14:38 ` [PATCH 2/8] sched: Track NUMA hinting faults on per-node basis Mel Gorman
2013-06-27 15:57 ` Peter Zijlstra
2013-06-28 12:22 ` Mel Gorman
2013-06-28 6:08 ` Srikar Dronamraju
2013-06-28 8:56 ` Peter Zijlstra
2013-06-28 12:30 ` Mel Gorman
2013-06-26 14:38 ` [PATCH 3/8] sched: Select a preferred node with the most numa hinting faults Mel Gorman
2013-06-28 6:14 ` Srikar Dronamraju
2013-06-28 8:59 ` Peter Zijlstra
2013-06-28 10:24 ` Srikar Dronamraju
2013-06-28 12:33 ` Mel Gorman
2013-06-26 14:38 ` [PATCH 4/8] sched: Update NUMA hinting faults once per scan Mel Gorman
2013-06-28 6:32 ` Srikar Dronamraju
2013-06-28 9:01 ` Peter Zijlstra
2013-06-26 14:38 ` [PATCH 5/8] sched: Favour moving tasks towards the preferred node Mel Gorman
2013-06-27 14:52 ` Peter Zijlstra
2013-06-27 14:53 ` Peter Zijlstra
2013-06-28 13:00 ` Mel Gorman
2013-06-27 16:01 ` Peter Zijlstra
2013-06-28 13:01 ` Mel Gorman
2013-06-27 16:11 ` Peter Zijlstra
2013-06-28 13:45 ` Mel Gorman [this message]
2013-06-28 15:10 ` Peter Zijlstra
2013-06-28 8:11 ` Srikar Dronamraju
2013-06-28 9:04 ` Peter Zijlstra
2013-06-28 10:07 ` Srikar Dronamraju
2013-06-28 10:24 ` Peter Zijlstra
2013-06-28 13:51 ` Mel Gorman
2013-06-28 17:14 ` Srikar Dronamraju
2013-06-28 17:34 ` Mel Gorman
2013-06-28 17:44 ` Srikar Dronamraju
2013-06-26 14:38 ` [PATCH 6/8] sched: Reschedule task on preferred NUMA node once selected Mel Gorman
2013-06-27 14:54 ` Peter Zijlstra
2013-06-28 13:54 ` Mel Gorman
2013-07-02 12:06 ` Srikar Dronamraju
2013-07-02 16:29 ` Mel Gorman
2013-07-02 18:17 ` Peter Zijlstra
2013-07-06 6:44 ` Srikar Dronamraju
2013-07-06 10:47 ` Peter Zijlstra
2013-07-02 18:15 ` Peter Zijlstra
2013-07-03 9:50 ` Peter Zijlstra
2013-07-03 15:28 ` Mel Gorman
2013-07-03 18:46 ` Peter Zijlstra
2013-06-26 14:38 ` [PATCH 7/8] sched: Split accounting of NUMA hinting faults that pass two-stage filter Mel Gorman
2013-06-27 14:56 ` Peter Zijlstra
2013-06-28 14:00 ` Mel Gorman
2013-06-28 7:00 ` Srikar Dronamraju
2013-06-28 9:36 ` Peter Zijlstra
2013-06-28 10:12 ` Srikar Dronamraju
2013-06-28 10:33 ` Peter Zijlstra
2013-06-28 14:29 ` Mel Gorman
2013-06-28 15:12 ` Peter Zijlstra
2013-06-26 14:38 ` [PATCH 8/8] sched: Increase NUMA PTE scanning when a new preferred node is selected Mel Gorman
2013-06-27 14:59 ` [PATCH 0/6] Basic scheduler support for automatic NUMA balancing Peter Zijlstra
2013-06-28 13:54 ` Srikar Dronamraju
2013-07-01 5:39 ` Srikar Dronamraju
2013-07-01 8:43 ` Mel Gorman
2013-07-02 5:28 ` Srikar Dronamraju
2013-07-02 7:46 ` Peter Zijlstra
2013-07-02 8:55 ` Peter Zijlstra
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