linux-kernel - Re: [PATCH 0/6] More graceful flusher thread memory reclaim wakeup

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: <20170920192909.GA27517@quad.stoffel.home>
Date:   Wed, 20 Sep 2017 15:29:09 -0400
From:   John Stoffel <john@...d.stoffel.home>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, hannes@...xchg.org, clm@...com, jack@...e.cz
Subject: Re: [PATCH 0/6] More graceful flusher thread memory reclaim wakeup

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.

John