From: Andreas Dilger <adilger@dilger.ca>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Li Wang <liwang@ubuntukylin.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Cong Wang <xiyou.wangcong@gmail.com>,
Zefan Li <lizefan@huawei.com>, Matthew Wilcox <matthew@wil.cx>
Subject: Re: [PATCH 0/3] Fadvise: Directory level page cache cleaning support
Date: Mon, 30 Dec 2013 12:40:05 -0700 [thread overview]
Message-ID: <FFE7C704-791E-4B73-9251-EFB9135AB254@dilger.ca> (raw)
In-Reply-To: <52C1C6F7.8010809@intel.com>
On Dec 30, 2013, at 12:18, Dave Hansen <dave.hansen@intel.com> wrote:
>
> Why is this necessary to do in the kernel? Why not leave it to
> userspace to walk the filesystem(s)?
I would suspect that trying to do it in userspace would be quite bad. It would require traversing the whole directory tree to issue cache flushed for each subdirectory, but it doesn't know when to stop traversal. That would mean the "cache flush" would turn into "cache pollute" and cause a lot of disk IO for subdirectories not in cache to begin with.
Cheers, Andreas
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next prev parent reply other threads:[~2013-12-30 19:40 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-30 13:45 Li Wang
2013-12-30 13:45 ` [PATCH 1/3] VFS: Add the declaration of shrink_pagecache_parent Li Wang
2013-12-30 13:45 ` [PATCH 2/3] Add shrink_pagecache_parent Li Wang
2014-01-02 23:55 ` Andrew Morton
2014-01-06 13:30 ` Dave Chinner
2014-01-08 2:06 ` Li Wang
2014-01-15 0:22 ` Dave Chinner
2013-12-30 13:45 ` [PATCH 3/3] Fadvise: Add the ability for directory level page cache cleaning Li Wang
2013-12-30 14:57 ` [PATCH 0/3] Fadvise: Directory level page cache cleaning support Matthew Wilcox
2013-12-30 19:18 ` Dave Hansen
2013-12-30 19:40 ` Andreas Dilger [this message]
2013-12-30 21:33 ` Dave Hansen
2014-01-02 12:44 ` Li Wang
2014-01-02 18:35 ` Dave Hansen
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