linux-kernel - Re: [PATCH v2 0/1] xen/blkback: Aggressively shrink page pools if a memory pressure is detected

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: <af195033-23d5-38ed-b73b-f6e2e3b34541@amazon.com>
Date:   Thu, 5 Dec 2019 16:16:19 +0100
From:   <sjpark@...zon.com>
To:     <axboe@...nel.dk>, <konrad.wilk@...cle.com>, <roger.pau@...rix.com>
CC:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <sj38.park@...il.com>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Subject: Re: [PATCH v2 0/1] xen/blkback: Aggressively shrink page pools if a
 memory pressure is detected

On 05.12.19 16:09, SeongJae Park wrote:
> Each `blkif` has a free pages pool for the grant mapping.  The size of
> the pool starts from zero and be increased on demand while processing
> the I/O requests.  If current I/O requests handling is finished or 100
> milliseconds has passed since last I/O requests handling, it checks and
> shrinks the pool to not exceed the size limit, `max_buffer_pages`.
>
> Therefore, `blkfront` running guests can cause a memory pressure in the
> `blkback` running guest by attaching a large number of block devices and
> inducing I/O.  System administrators can avoid such problematic
> situations by limiting the maximum number of devices each guest can
> attach.  However, finding the optimal limit is not so easy.  Improper
> set of the limit can result in the memory pressure or a resource
> underutilization.  This commit avoids such problematic situations by
> shrinking the pools aggressively (further the limit) for a while (users
> can set this duration via a module parameter) if a memory pressure is
> detected.
>
>
> Base Version
> ------------
>
> This patch is based on v5.4.  A complete tree is also available at my
> public git repo:
> https://github.com/sjp38/linux/tree/blkback_aggressive_shrinking_v2
>
>
> Patch History
> -------------
>
> Changes from v1 (https://lore.kernel.org/xen-devel/20191204113419.2298-1-sjpark@amazon.com/)
>  - Adjust the description to not use the term, `arbitrarily` (suggested
>    by Paul Durrant)
>  - Specify time unit of the duration in the parameter description,
>    (suggested by Maximilian Heyne)
>  - Change default aggressive shrinking duration from 1ms to 10ms
>  - Merged two patches into one single patch
>
>
> SeongJae Park (1):
>   xen/blkback: Aggressively shrink page pools if a memory pressure is
>     detected
>
>  drivers/block/xen-blkback/blkback.c | 35 +++++++++++++++++++++++++++--
>  1 file changed, 33 insertions(+), 2 deletions(-)


CC-ing xen-devel@...ts.xenproject.org


Thanks,
SeongJae Park

>