From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-1?Q?C=E9dric_Villemain?= Subject: Re: [PATCH] fs: add fincore(2) (mincore(2) for file descriptors) Date: Sat, 8 May 2010 00:46:37 +0200 Message-ID: References: <20100216181312.GA9700@frostnet.net> <20100221030238.GA26511@hexapodia.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: Chris Frost , Andi Kleen , Wu Fengguang , Andrew Morton , Heiko Carstens , Alexander Viro , Benny Halevy , Andrew@firstfloor.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Steve VanDeBogart , linux-fsdevel@vger.kernel.org, Matt Mackall , Peter Zijlstra To: Andy Isaacson Return-path: In-Reply-To: <20100221030238.GA26511@hexapodia.org> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org 2010/2/21 Andy Isaacson : > On Tue, Feb 16, 2010 at 10:13:12AM -0800, Chris Frost wrote: >> Add the fincore() system call. fincore() is mincore() for file descripto= rs. >> >> The functionality of fincore() can be emulated with an mmap(), mincore()= , >> and munmap(), but this emulation requires more system calls and requires >> page table modifications. fincore() can provide a significant performanc= e >> improvement for non-sequential in-core queries. > > In addition to being expensive, mmap/mincore/munmap perturb the VM's > eviction algorithm -- a page is less likely to be evicted if it's > mmapped when being considered for eviction. > > I frequently see this happen when using mincore(1) from > http://bitbucket.org/radii/mincore/ -- "watch mincore -v *.big" while > *.big are being sequentially read results in a significant number of > pages remaining in-core, whereas if I only run mincore after the > sequential read is complete, the large files will be nearly-completely > out of core (except for the tail of the last file, of course). > > It's very interesting to watch > % watch --interval=3D.5 mincore -v * > > while an IO-intensive process is happening, such as mke2fs on a > filesystem image. > > So, I support the addition of fincore(2) and would use it if it were > merged. I wonder what the actual state is for this proposition? I'd like to see fincore(2) added too... > > -andy > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" = in > the body of a message to majordomo@vger.kernel.org > More majordomo info at =A0http://vger.kernel.org/majordomo-info.html > --=20 C=E9dric Villemain -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org