From: Vlastimil Babka <vbabka@suse.cz>
To: Mike Kravetz <mike.kravetz@oracle.com>,
Hillf Danton <hdanton@sina.com>, Mel Gorman <mgorman@suse.de>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Michal Hocko <mhocko@kernel.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH 1/3] mm, reclaim: make should_continue_reclaim perform dryrun detection
Date: Thu, 1 Aug 2019 10:44:44 +0200 [thread overview]
Message-ID: <60b15fed-2110-c783-d48c-20a1d45f354d@suse.cz> (raw)
In-Reply-To: <f6e25e52-bb02-6d79-b9fd-3acc8358ec45@oracle.com>
On 7/31/19 11:11 PM, Mike Kravetz wrote:
> On 7/31/19 4:08 AM, Vlastimil Babka wrote:
>>
>> I agree this is an improvement overall, but perhaps the patch does too
>> many things at once. The reshuffle is one thing and makes sense. The
>> change of the last return condition could perhaps be separate. Also
>> AFAICS the ultimate result is that when nr_reclaimed == 0, the function
>> will now always return false. Which makes the initial test for
>> __GFP_RETRY_MAYFAIL and the comments there misleading. There will no
>> longer be a full LRU scan guaranteed - as long as the scanned LRU chunk
>> yields no reclaimed page, we abort.
>
> Can someone help me understand why nr_scanned == 0 guarantees a full
> LRU scan? FWICS, nr_scanned used in this context is only incremented
> in shrink_page_list and potentially shrink_zones. In the stall case I
> am looking at, there are MANY cases in which nr_scanned is only a few
> pages and none of those are reclaimed.
>
> Can we not get nr_scanned == 0 on an arbitrary chunk of the LRU?
>
> I must be missing something, because I do not see how nr_scanned == 0
> guarantees a full scan.
Yeah, seems like it doesn't. More reasons to update/remove the comment.
Can be a followup cleanup if you don't want to block the series.
next prev parent reply other threads:[~2019-08-01 8:44 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-24 17:50 [RFC PATCH 0/3] fix hugetlb page allocation stalls Mike Kravetz
2019-07-24 17:50 ` [RFC PATCH 1/3] mm, reclaim: make should_continue_reclaim perform dryrun detection Mike Kravetz
2019-07-25 8:05 ` Mel Gorman
2019-07-26 8:12 ` Mel Gorman
2019-07-31 11:08 ` Vlastimil Babka
2019-07-31 12:25 ` Mel Gorman
2019-07-31 21:11 ` Mike Kravetz
2019-08-01 8:44 ` Vlastimil Babka [this message]
2019-07-24 17:50 ` [RFC PATCH 2/3] mm, compaction: use MIN_COMPACT_COSTLY_PRIORITY everywhere for costly orders Mike Kravetz
2019-07-25 8:06 ` Mel Gorman
2019-07-31 12:06 ` Vlastimil Babka
2019-07-31 20:30 ` Mike Kravetz
2019-08-01 13:01 ` Vlastimil Babka
2019-08-01 20:33 ` Mike Kravetz
2019-08-02 10:20 ` Vlastimil Babka
2019-08-02 12:05 ` Vlastimil Babka
2019-08-02 17:44 ` Mike Kravetz
2019-07-24 17:50 ` [RFC PATCH 3/3] hugetlbfs: don't retry when pool page allocations start to fail Mike Kravetz
2019-07-25 8:13 ` Mel Gorman
2019-07-25 17:15 ` Mike Kravetz
2019-07-25 22:43 ` Mel Gorman
2019-07-31 13:23 ` Vlastimil Babka
2019-07-31 21:13 ` Mike Kravetz
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