From: Chengguang Xu <cgxu519@mykernel.net>
To: "Jan Kara" <jack@suse.cz>
Cc: "Miklos Szeredi" <miklos@szeredi.hu>,
"Amir Goldstein" <amir73il@gmail.com>,
"linux-fsdevel" <linux-fsdevel@vger.kernel.org>,
"overlayfs" <linux-unionfs@vger.kernel.org>,
"linux-kernel" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH v5 06/10] ovl: implement overlayfs' ->write_inode operation
Date: Fri, 19 Nov 2021 14:12:46 +0800 [thread overview]
Message-ID: <17d36d37022.1227b6f102736.1047689367927335302@mykernel.net> (raw)
In-Reply-To: <20211118164349.GB8267@quack2.suse.cz>
---- 在 星期五, 2021-11-19 00:43:49 Jan Kara <jack@suse.cz> 撰写 ----
> On Thu 18-11-21 20:02:09, Chengguang Xu wrote:
> > ---- 在 星期四, 2021-11-18 19:23:15 Jan Kara <jack@suse.cz> 撰写 ----
> > > On Thu 18-11-21 14:32:36, Chengguang Xu wrote:
> > > >
> > > > ---- 在 星期三, 2021-11-17 14:11:29 Chengguang Xu <cgxu519@mykernel.net> 撰写 ----
> > > > > ---- 在 星期二, 2021-11-16 20:35:55 Miklos Szeredi <miklos@szeredi.hu> 撰写 ----
> > > > > > On Tue, 16 Nov 2021 at 03:20, Chengguang Xu <cgxu519@mykernel.net> wrote:
> > > > > > >
> > > > > > > ---- 在 星期四, 2021-10-07 21:34:19 Miklos Szeredi <miklos@szeredi.hu> 撰写 ----
> > > > > > > > On Thu, 7 Oct 2021 at 15:10, Chengguang Xu <cgxu519@mykernel.net> wrote:
> > > > > > > > > > However that wasn't what I was asking about. AFAICS ->write_inode()
> > > > > > > > > > won't start write back for dirty pages. Maybe I'm missing something,
> > > > > > > > > > but there it looks as if nothing will actually trigger writeback for
> > > > > > > > > > dirty pages in upper inode.
> > > > > > > > > >
> > > > > > > > >
> > > > > > > > > Actually, page writeback on upper inode will be triggered by overlayfs ->writepages and
> > > > > > > > > overlayfs' ->writepages will be called by vfs writeback function (i.e writeback_sb_inodes).
> > > > > > > >
> > > > > > > > Right.
> > > > > > > >
> > > > > > > > But wouldn't it be simpler to do this from ->write_inode()?
> > > > > > > >
> > > > > > > > I.e. call write_inode_now() as suggested by Jan.
> > > > > > > >
> > > > > > > > Also could just call mark_inode_dirty() on the overlay inode
> > > > > > > > regardless of the dirty flags on the upper inode since it shouldn't
> > > > > > > > matter and results in simpler logic.
> > > > > > > >
> > > > > > >
> > > > > > > Hi Miklos,
> > > > > > >
> > > > > > > Sorry for delayed response for this, I've been busy with another project.
> > > > > > >
> > > > > > > I agree with your suggesion above and further more how about just mark overlay inode dirty
> > > > > > > when it has upper inode? This approach will make marking dirtiness simple enough.
> > > > > >
> > > > > > Are you suggesting that all non-lower overlay inodes should always be dirty?
> > > > > >
> > > > > > The logic would be simple, no doubt, but there's the cost to walking
> > > > > > those overlay inodes which don't have a dirty upper inode, right?
> > > > >
> > > > > That's true.
> > > > >
> > > > > > Can you quantify this cost with a benchmark? Can be totally synthetic,
> > > > > > e.g. lookup a million upper files without modifying them, then call
> > > > > > syncfs.
> > > > > >
> > > > >
> > > > > No problem, I'll do some tests for the performance.
> > > > >
> > > >
> > > > Hi Miklos,
> > > >
> > > > I did some rough tests and the results like below. In practice, I don't
> > > > think that 1.3s extra time of syncfs will cause significant problem.
> > > > What do you think?
> > >
> > > Well, burning 1.3s worth of CPU time for doing nothing seems like quite a
> > > bit to me. I understand this is with 1000000 inodes but although that is
> > > quite a few it is not unheard of. If there would be several containers
> > > calling sync_fs(2) on the machine they could easily hog the machine... That
> > > is why I was originally against keeping overlay inodes always dirty and
> > > wanted their dirtiness to at least roughly track the real need to do
> > > writeback.
> > >
> >
> > Hi Jan,
> >
> > Actually, the time on user and sys are almost same with directly excute syncfs on underlying fs.
> > IMO, it only extends syncfs(2) waiting time for perticular container but not burning cpu.
> > What am I missing?
>
> Ah, right, I've missed that only realtime changed, not systime. I'm sorry
> for confusion. But why did the realtime increase so much? Are we waiting
> for some IO?
>
There are many places to call cond_resched() in writeback process,
so sycnfs process was scheduled several times.
Thanks,
Chengguang
next prev parent reply other threads:[~2021-11-19 6:13 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-23 13:08 [RFC PATCH v5 00/10] implement containerized syncfs for overlayfs Chengguang Xu
2021-09-23 13:08 ` [RFC PATCH v5 01/10] ovl: setup overlayfs' private bdi Chengguang Xu
2021-09-23 13:08 ` [RFC PATCH v5 02/10] ovl: implement ->writepages operation Chengguang Xu
2021-09-23 13:08 ` [RFC PATCH v5 03/10] ovl: implement overlayfs' ->evict_inode operation Chengguang Xu
2021-10-06 15:33 ` Miklos Szeredi
2021-10-07 6:08 ` Chengguang Xu
2021-10-07 7:43 ` Miklos Szeredi
2021-09-23 13:08 ` [RFC PATCH v5 04/10] ovl: mark overlayfs' inode dirty on modification Chengguang Xu
2021-10-07 18:43 ` Miklos Szeredi
2021-09-23 13:08 ` [RFC PATCH v5 05/10] ovl: mark overlayfs' inode dirty on shared mmap Chengguang Xu
2021-09-23 13:08 ` [RFC PATCH v5 06/10] ovl: implement overlayfs' ->write_inode operation Chengguang Xu
2021-10-07 9:01 ` Jan Kara
2021-10-07 12:26 ` Chengguang Xu
2021-10-07 14:41 ` Jan Kara
2021-10-07 14:54 ` Chengguang Xu
2021-10-07 9:23 ` Miklos Szeredi
2021-10-07 12:28 ` Chengguang Xu
2021-10-07 12:45 ` Miklos Szeredi
2021-10-07 13:09 ` Chengguang Xu
2021-10-07 13:34 ` Miklos Szeredi
2021-10-07 14:46 ` Jan Kara
2021-10-07 14:53 ` Chengguang Xu
2021-10-07 18:51 ` Miklos Szeredi
2021-10-08 13:13 ` Jan Kara
2021-11-16 2:20 ` Chengguang Xu
2021-11-16 12:35 ` Miklos Szeredi
2021-11-17 6:11 ` Chengguang Xu
2021-11-18 6:32 ` Chengguang Xu
2021-11-18 11:23 ` Jan Kara
2021-11-18 12:02 ` Chengguang Xu
2021-11-18 16:43 ` Jan Kara
2021-11-19 6:12 ` Chengguang Xu [this message]
2021-11-30 11:22 ` Jan Kara
2021-11-30 16:09 ` Chengguang Xu
2021-11-30 19:04 ` Amir Goldstein
2021-12-01 2:37 ` Chengguang Xu
2021-12-01 6:31 ` Chengguang Xu
2021-12-01 7:19 ` Amir Goldstein
2021-12-01 13:46 ` Jan Kara
2021-12-01 14:59 ` Chengguang Xu
2021-12-01 16:24 ` Chengguang Xu
2021-12-01 22:47 ` Amir Goldstein
2021-12-01 23:23 ` ovl_flush() behavior Amir Goldstein
2021-12-02 2:11 ` Chengguang Xu
2021-12-02 15:20 ` Vivek Goyal
2021-12-02 15:59 ` Amir Goldstein
2021-12-02 22:00 ` Vivek Goyal
2021-12-02 15:14 ` Vivek Goyal
2021-12-05 14:06 ` [RFC PATCH v5 06/10] ovl: implement overlayfs' ->write_inode operation Chengguang Xu
2021-12-07 5:33 ` Amir Goldstein
2022-02-05 16:09 ` Chengguang Xu
2022-02-05 16:23 ` Amir Goldstein
2021-09-23 13:08 ` [RFC PATCH v5 07/10] ovl: cache dirty overlayfs' inode Chengguang Xu
2021-10-07 11:09 ` Miklos Szeredi
2021-10-07 12:04 ` Chengguang Xu
2021-10-07 12:27 ` Miklos Szeredi
2021-09-23 13:08 ` [RFC PATCH v5 08/10] fs: export wait_sb_inodes() Chengguang Xu
2021-09-23 13:08 ` [RFC PATCH v5 09/10] fs: introduce new helper sync_fs_and_blockdev() Chengguang Xu
2021-10-19 7:15 ` Amir Goldstein
2021-11-15 11:39 ` Chengguang Xu
2021-09-23 13:08 ` [RFC PATCH v5 10/10] ovl: implement containerized syncfs for overlayfs Chengguang Xu
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=17d36d37022.1227b6f102736.1047689367927335302@mykernel.net \
--to=cgxu519@mykernel.net \
--cc=amir73il@gmail.com \
--cc=jack@suse.cz \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-unionfs@vger.kernel.org \
--cc=miklos@szeredi.hu \
/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).