linux-kernel - Re: A mainline question about cgroup writeback

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Message-ID: <CAGjg+kEnEiqwMiAofh1otK4gVPb8WqwNkQZjTBamqj1HWOYMig@mail.gmail.com>
Date:	Wed, 20 Apr 2016 14:32:55 +0800
From:	Alex Shi <lkml.alex@...il.com>
To:	zhong jiang <zhongjiang@...wei.com>
Cc:	Tejun Heo <tj@...nel.org>, Miao Xie <miaoxie@...wei.com>,
	lizefan@...wei.com, dingxiang@...wei.com,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: A mainline question about cgroup writeback

It looks like a bug on cgroup writeback. Is this a regression or
consistent issue? If it's a regression, you may could do bisect to
find out the buggy commit.

On Tue, Apr 19, 2016 at 3:19 PM, zhong jiang <zhongjiang@...wei.com> wrote:
> cgroup writeback support the filesystem both ext4 and ext2.
> but,  it appears to be not work when I test the function in the ext4.
> The example is as follows:
> echo "8:0 1048576" > blkio.throttle.write_bps_device
> echo $$ > cgroup.procs
> dd if=/dev/zero of=/test.c bs=1M count=10240
> 10240+0 records in
> 10240+0 records out
> 10737418240 bytes (11 GB) copied, 49.8796 s, 215 MB/s
>
> Furthering test find that the ratelimit will be limited if it write data
> to disk directly.  Additionly, The read ratelimit is limited whther it go through
> the page cache or not.
>
> The kernel version is 4.6  I have tested,  And the corresponding files
> in the attachment



-- 
Thanks
    Alex