linux-kernel - Re: [PATCH 0/5] VFS: Directory level cache cleaning

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Date:	Tue, 17 Dec 2013 11:08:16 +0800
From:	Li Wang <liwang@...ntukylin.com>
To:	Cong Wang <xiyou.wangcong@...il.com>
CC:	Alexander Viro <viro@...iv.linux.org.uk>,
	Sage Weil <sage@...tank.com>, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
	Yunchuan Wen <yunchuanwen@...ntukylin.com>
Subject: Re: [PATCH 0/5] VFS: Directory level cache cleaning

As far as we know, fadvise(DONTNEED) does not support metadata
cache cleaning. We think that is desirable under massive small files
situations. Another thing is that do people accept the behavior
of feeding a directory fd to fadvise will recusively clean all
page caches of files inside that directory?

On 2013/12/17 1:45, Cong Wang wrote:
> On Mon, Dec 16, 2013 at 7:00 AM, Li Wang <liwang@...ntukylin.com> wrote:
>> This patch extend the 'drop_caches' interface to
>> support directory level cache cleaning and has a complete
>> backward compatibility. '{1,2,3}' keeps the same semantics
>> as before. Besides, "{1,2,3}:DIRECTORY_PATH_NAME" is allowed
>> to recursively clean the caches under DIRECTORY_PATH_NAME.
>> For example, 'echo 1:/home/foo/jpg > /proc/sys/vm/drop_caches'
>> will clean the page caches of the files inside 'home/foo/jpg'.
>>
>
> This interface is ugly...
>
> And we already have a file-level drop cache, that is,
> fadvise(DONTNEED). Can you extend it if it can't
> handle a directory fd?
>
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