linux-kernel - Re: [patch 0/3] mm: improve page aging fairness between zones/nodes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <51F8D9F3.4040108@bitsync.net>
Date:	Wed, 31 Jul 2013 11:33:39 +0200
From:	Zlatko Calusic <zcalusic@...sync.net>
To:	Johannes Weiner <hannes@...xchg.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 0/3] mm: improve page aging fairness between zones/nodes

On 24.07.2013 13:18, Zlatko Calusic wrote:
> On 22.07.2013 18:48, Zlatko Calusic wrote:
>> On 19.07.2013 22:55, Johannes Weiner wrote:
>>> The way the page allocator interacts with kswapd creates aging
>>> imbalances, where the amount of time a userspace page gets in memory
>>> under reclaim pressure is dependent on which zone, which node the
>>> allocator took the page frame from.
>>>
>>> #1 fixes missed kswapd wakeups on NUMA systems, which lead to some
>>>     nodes falling behind for a full reclaim cycle relative to the other
>>>     nodes in the system
>>>
>>> #3 fixes an interaction where kswapd and a continuous stream of page
>>>     allocations keep the preferred zone of a task between the high and
>>>     low watermark (allocations succeed + kswapd does not go to sleep)
>>>     indefinitely, completely underutilizing the lower zones and
>>>     thrashing on the preferred zone
>>>
>>> These patches are the aging fairness part of the thrash-detection
>>> based file LRU balancing.  Andrea recommended to submit them
>>> separately as they are bugfixes in their own right.
>>>
>>
>> I have the patch applied and under testing. So far, so good. It looks
>> like it could finally fix the bug that I was chasing few months ago
>> (nicely described in your bullet #3). But, few more days of testing will
>> be needed before I can reach a quality verdict.
>>
>
> Well, only 2 days later it's already obvious that the patch is perfect! :)
>

Additionaly, on the patched kernel, kswapd burns 30% less CPU cycles. 
Nice to see that restored balance also eases kswapd's job, but that was 
to be expected. Measured on the real workload, twice, to be sure.

Regards,
-- 
Zlatko

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/