linux-kernel - Re: [PATCH v2 block 1/2] writeback, cgroup: Adjust WB_FRN_TIME_CUT_DIV to accelerate foreign inode switching

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] [day] [month] [year] [list]

Date:   Thu, 15 Aug 2019 13:31:02 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Tejun Heo <tj@...nel.org>, Jan Kara <jack@...e.cz>
Cc:     linux-block@...r.kernel.org, kernel-team@...com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 block 1/2] writeback, cgroup: Adjust
 WB_FRN_TIME_CUT_DIV to accelerate foreign inode switching

On 8/15/19 1:25 PM, Tejun Heo wrote:
> WB_FRN_TIME_CUT_DIV is used to tell the foreign inode detection logic
> to ignore short writeback rounds to prevent getting confused by a
> burst of short writebacks.  The parameter is currently 2 meaning that
> anything smaller than half of the running average writback duration
> will be ignored.
> 
> This is unnecessarily aggressive.  The detection logic uses 16 history
> slots and is already reasonably protected against some short bursts
> confusing it and the current parameter can lead to tens of seconds of
> missed detection depending on the writeback pattern.
> 
> Let's change the parameter to 8, so that it only ignores writeback
> with are smaller than 12.5% of the current running average.
> 
> v2: Add comment explaining what's going on with the foreign detection
>      parameters.

Applied 1-2 for 5.4, thanks.

-- 
Jens Axboe