From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
To: Cong Wang <amwang@redhat.com>
Cc: "Pádraig Brady" <P@draigBrady.com>,
linux-kernel@vger.kernel.org,
"Andrew Morton" <akpm@linux-foundation.org>,
"Cong Wang" <xiyou.wangcong@gmail.com>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
"Matthew Wilcox" <matthew@wil.cx>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
kosaki.motohiro@gmail.com
Subject: Re: [RFC Patch] fs: implement per-file drop caches
Date: Thu, 31 May 2012 02:30:22 -0400 [thread overview]
Message-ID: <4FC70FFE.50809@gmail.com> (raw)
In-Reply-To: <1338445233.19369.21.camel@cr0>
(5/31/12 2:20 AM), Cong Wang wrote:
> On Wed, 2012-05-30 at 16:14 +0100, Pádraig Brady wrote:
>> On 05/30/2012 02:38 PM, Cong Wang wrote:
>>> This is a draft patch of implementing per-file drop caches.
>>>
>>> It introduces a new fcntl command F_DROP_CACHES to drop
>>> file caches of a specific file. The reason is that currently
>>> we only have a system-wide drop caches interface, it could
>>> cause system-wide performance down if we drop all page caches
>>> when we actually want to drop the caches of some huge file.
>>
>> This is useful functionality.
>> Though isn't it already provided with POSIX_FADV_DONTNEED?
>
> Thanks for teaching this!
>
> However, from the source code of madvise_dontneed() it looks like it is
> using a totally different way to drop page caches, that is to invalidate
> the page mapping, and trigger a re-mapping of the file pages after a
> page fault. So, yeah, this could probably drop the page caches too (I am
> not so sure, haven't checked the code in details), but with my patch, it
> flushes the page caches directly, what's more, it can also prune
> dcache/icache of the file.
madvise should work. I don't think we need duplicate interface. Moreomover
madvise(2) is cleaner than fcntl(2).
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next prev parent reply other threads:[~2012-05-31 6:30 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-30 13:38 [RFC Patch] fs: implement per-file drop caches Cong Wang
2012-05-30 15:12 ` John Stoffel
2012-05-31 6:28 ` Cong Wang
2012-05-30 15:14 ` Pádraig Brady
2012-05-31 6:20 ` Cong Wang
2012-05-31 6:30 ` KOSAKI Motohiro [this message]
2012-05-31 12:11 ` Cong Wang
2012-05-31 19:09 ` KOSAKI Motohiro
2012-06-01 11:32 ` Cong Wang
2012-06-01 13:08 ` John Stoffel
2012-06-04 3:28 ` Cong Wang
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