Messages in this thread | | | Date | Fri, 06 Jun 2014 14:23:41 -0400 | From | Rik van Riel <> | Subject | Re: [PATCH] sched,numa: always try to migrate to preferred node at task_numa_placement time |
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On 06/06/2014 01:18 PM, Peter Zijlstra wrote: > On Wed, Jun 04, 2014 at 04:33:15PM -0400, Rik van Riel wrote: >> It is possible that at task_numa_placement time, the task's >> numa_preferred_nid does not change, but the task is not >> actually running on the preferred node at the time. >> >> In that case, we still want to attempt migration to the >> preferred node. > > So we have that numa_migrate_retry which was supposed to keep kicking > the task until it got where it needed to go.
It does, and it appears to work.
> But now you continuously kick from task_numa_placement().
No, we only kick from task_numa_placement() if the task is not already running on its preferred nid.
> Clearly the retry thing didn't work, what happened? We got to the > preferred nid, disabled the retry and got moved away again? > > Do we want to remove the retry logic in favour of this more aggressive > form?
I think we want both. When we have fresh statistics, and we discover that we are not running on our preferred nid, is there any reason not to relocate to a better node?
Moving a task to another node is cheap, and moving it sooner means we can end up avoiding migrating memory around twice.
>> @@ -1575,11 +1575,13 @@ static void task_numa_placement(struct task_struct *p) > >> + if (max_faults) { >> + /* Set the new preferred node */ >> + if (max_nid != p->numa_preferred_nid) >> + sched_setnuma(p, max_nid); >> + >> + if (task_node(p) != p->numa_preferred_nid) >> + numa_migrate_preferred(p); >> } >> > >
-- All rights reversed
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