linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: Tejun Heo <tj@kernel.org>
To: zhangliguang <zhangliguang@linux.alibaba.com>
Cc: akpm@linux-foundation.org, cgroups@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] fs/writeback: Attach inode's wb to root if needed
Date: Thu, 9 May 2019 09:48:02 -0700	[thread overview]
Message-ID: <20190509164802.GV374014@devbig004.ftw2.facebook.com> (raw)
In-Reply-To: <1557389033-39649-1-git-send-email-zhangliguang@linux.alibaba.com>

Hello,

On Thu, May 09, 2019 at 04:03:53PM +0800, zhangliguang wrote:
> There might have tons of files queued in the writeback, awaiting for
> writing back. Unfortunately, the writeback's cgroup has been dead. In
> this case, we reassociate the inode with another writeback cgroup, but
> we possibly can't because the writeback associated with the dead cgroup
> is the only valid one. In this case, the new writeback is allocated,
> initialized and associated with the inode. It causes unnecessary high
> system load and latency.
> 
> This fixes the issue by enforce moving the inode to root cgroup when the
> previous binding cgroup becomes dead. With it, no more unnecessary
> writebacks are created, populated and the system load decreased by about
> 6x in the online service we encounted:
>     Without the patch: about 30% system load
>     With the patch:    about  5% system load

Can you please describe the scenario with more details?  I'm having a
bit of hard time understanding the amount of cpu cycles being
consumed.

Thanks.

-- 
tejun


  reply	other threads:[~2019-05-09 16:48 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-09  8:03 [PATCH] fs/writeback: Attach inode's wb to root if needed zhangliguang
2019-05-09 16:48 ` Tejun Heo [this message]
2019-05-10  1:54   ` 乱石
2019-05-13 18:30     ` Dennis Zhou
2019-05-16  5:54       ` 乱石

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190509164802.GV374014@devbig004.ftw2.facebook.com \
    --to=tj@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=cgroups@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=zhangliguang@linux.alibaba.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).