Messages in this thread | | | Date | Wed, 06 May 2015 11:28:12 +0200 | From | Vlastimil Babka <> | Subject | Re: [PATCH v2] mm: vmscan: do not throttle based on pfmemalloc reserves if node has no reclaimable pages |
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On 05/06/2015 12:09 AM, Nishanth Aravamudan wrote: > On 03.04.2015 [10:45:56 -0700], Nishanth Aravamudan wrote: >>> What I find somewhat worrying though is that we could potentially >>> break the pfmemalloc_watermark_ok() test in situations where >>> zone_reclaimable_pages(zone) == 0 is a transient situation (and not >>> a permanently allocated hugepage). In that case, the throttling is >>> supposed to help system recover, and we might be breaking that >>> ability with this patch, no? >> >> Well, if it's transient, we'll skip it this time through, and once there >> are reclaimable pages, we should notice it again. >> >> I'm not familiar enough with this logic, so I'll read through the code >> again soon to see if your concern is valid, as best I can. > > In reviewing the code, I think that transiently unreclaimable zones will > lead to some higher direct reclaim rates and possible contention, but > shouldn't cause any major harm. The likelihood of that situation, as > well, in a non-reserved memory setup like the one I described, seems > exceedingly low.
OK, I guess when a reasonably configured system has nothing to reclaim, it's already busted and throttling won't change much.
Consider the patch Acked-by: Vlastimil Babka <vbabka@suse.cz>
> Thanks, > Nish >
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