From: Jens Axboe <axboe@kernel.dk>
To: John Stoffel <john@quad.stoffel.home>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, hannes@cmpxchg.org, clm@fb.com, jack@suse.cz
Subject: Re: [PATCH 0/6] More graceful flusher thread memory reclaim wakeup
Date: Wed, 20 Sep 2017 13:32:25 -0600 [thread overview]
Message-ID: <8a91a54e-e224-ad79-faac-3f8fe654246a@kernel.dk> (raw)
In-Reply-To: <20170920192909.GA27517@quad.stoffel.home>
On 09/20/2017 01:29 PM, John Stoffel wrote:
> On Tue, Sep 19, 2017 at 01:53:01PM -0600, Jens Axboe wrote:
>> We've had some issues with writeback in presence of memory reclaim
>> at Facebook, and this patch set attempts to fix it up. The real
>> functional change is the last patch in the series, the first 5 are
>> prep and cleanup patches.
>>
>> The basic idea is that we have callers that call
>> wakeup_flusher_threads() with nr_pages == 0. This means 'writeback
>> everything'. For memory reclaim situations, we can end up queuing
>> a TON of these kinds of writeback units. This can cause softlockups
>> and further memory issues, since we allocate huge amounts of
>> struct wb_writeback_work to handle this writeback. Handle this
>> situation more gracefully.
>
> This looks nice, but do you have any numbers to show how this improves
> things? I read the patches, but I'm not strong enough to comment on
> them at all. But I am interested in how this improves writeback under
> pressure, if at all.
Writeback should be about the same, it's mostly about preventing
softlockups and excessive memory usage, under conditions where we are
actively trying to reclaim/clean memory. It was bad enough to cause
softlockups for writeback work processing, while the pending writeback
work units grew to insane lengths.
--
Jens Axboe
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next prev parent reply other threads:[~2017-09-20 19:32 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-19 19:53 [PATCH 0/6] More graceful flusher thread memory reclaim wakeup Jens Axboe
2017-09-19 19:53 ` [PATCH 1/6] buffer: cleanup free_more_memory() flusher wakeup Jens Axboe
2017-09-19 20:05 ` Johannes Weiner
2017-09-20 14:17 ` Jan Kara
2017-09-20 15:18 ` Jens Axboe
2017-09-19 19:53 ` [PATCH 2/6] fs-writeback: provide a wakeup_flusher_threads_bdi() Jens Axboe
2017-09-19 20:05 ` Johannes Weiner
2017-09-20 14:19 ` Jan Kara
2017-09-19 19:53 ` [PATCH 3/6] page-writeback: pass in '0' for nr_pages writeback in laptop mode Jens Axboe
2017-09-19 20:06 ` Johannes Weiner
2017-09-20 14:35 ` Jan Kara
2017-09-20 15:19 ` Jens Axboe
2017-09-19 19:53 ` [PATCH 4/6] fs-writeback: make wb_start_writeback() static Jens Axboe
2017-09-19 20:07 ` Johannes Weiner
2017-09-20 14:35 ` Jan Kara
2017-09-19 19:53 ` [PATCH 5/6] fs-writeback: move nr_pages == 0 logic to one location Jens Axboe
2017-09-19 20:07 ` Johannes Weiner
2017-09-20 14:41 ` Jan Kara
2017-09-20 15:05 ` Jens Axboe
2017-09-20 15:36 ` Jan Kara
2017-09-20 15:40 ` Jens Axboe
2017-09-19 19:53 ` [PATCH 6/6] fs-writeback: only allow one inflight and pending !nr_pages flush Jens Axboe
2017-09-19 20:18 ` Johannes Weiner
2017-09-19 20:39 ` Jens Axboe
2017-09-20 1:57 ` Jens Axboe
2017-09-20 3:10 ` Amir Goldstein
2017-09-20 4:13 ` Jens Axboe
2017-09-20 6:05 ` Amir Goldstein
2017-09-20 12:35 ` Jens Axboe
2017-09-20 14:43 ` Jan Kara
2017-09-20 19:29 ` [PATCH 0/6] More graceful flusher thread memory reclaim wakeup John Stoffel
2017-09-20 19:32 ` Jens Axboe [this message]
2017-09-20 23:11 ` Johannes Weiner
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