From: Vlastimil Babka <vbabka@suse.cz>
To: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@suse.cz>,
Dave Hansen <dave.hansen@intel.com>, Mel Gorman <mgorman@suse.de>,
anton@sambar.org, linuxppc-dev@lists.ozlabs.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Rik van Riel <riel@redhat.com>, Dan Streetman <ddstreet@ieee.org>
Subject: Re: [PATCH v2] mm: vmscan: do not throttle based on pfmemalloc reserves if node has no reclaimable pages
Date: Wed, 06 May 2015 11:28:12 +0200 [thread overview]
Message-ID: <5549DEAC.6080709@suse.cz> (raw)
In-Reply-To: <20150505220913.GC32719@linux.vnet.ibm.com>
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
>
next prev parent reply other threads:[~2015-05-06 9:28 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-27 19:28 [PATCH] mm: vmscan: do not throttle based on pfmemalloc reserves if node has no reclaimable zones Nishanth Aravamudan
2015-03-27 19:39 ` Nishanth Aravamudan
2015-03-27 19:58 ` Dan Streetman
2015-03-27 20:17 ` Dave Hansen
2015-03-27 22:23 ` [PATCH v2] mm: vmscan: do not throttle based on pfmemalloc reserves if node has no reclaimable pages Nishanth Aravamudan
2015-03-31 9:48 ` Michal Hocko
2015-04-03 7:57 ` Vlastimil Babka
2015-04-03 17:45 ` Nishanth Aravamudan
2015-05-05 22:09 ` Nishanth Aravamudan
2015-05-06 9:28 ` Vlastimil Babka [this message]
2015-05-08 22:47 ` Andrew Morton
2015-05-08 23:18 ` Nishanth Aravamudan
2015-04-03 17:43 ` Nishanth Aravamudan
2015-04-03 18:24 ` Michal Hocko
2015-04-03 18:50 ` Nishanth Aravamudan
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