lkml.org 
[lkml]   [2012]   [May]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [RFC Patch] fs: implement per-file drop caches
From
Date
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.

Cheers.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2012-05-31 09:01    [W:3.505 / U:0.056 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site