Return-Path: Received: from mail-vx0-f174.google.com ([209.85.220.174]:39071 "EHLO mail-vx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752525Ab1FIOzK convert rfc822-to-8bit (ORCPT ); Thu, 9 Jun 2011 10:55:10 -0400 Received: by vxi39 with SMTP id 39so1231524vxi.19 for ; Thu, 09 Jun 2011 07:55:09 -0700 (PDT) In-Reply-To: <4DF062D6.7010304@panasas.com> References: <09142112ff0115f7f22124a69ead7b9bb5e0958f.1307464382.git.rees@umich.edu> <4DEED80A.4000102@panasas.com> <20110608021852.GA20998@merit.edu> <4DF062D6.7010304@panasas.com> From: Peng Tao Date: Thu, 9 Jun 2011 22:54:48 +0800 Message-ID: Subject: Re: [PATCH 87/88] Add configurable prefetch size for layoutget To: Benny Halevy Cc: Jim Rees , linux-nfs@vger.kernel.org, peter honeyman Content-Type: text/plain; charset=UTF-8 Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Thu, Jun 9, 2011 at 2:06 PM, Benny Halevy wrote: > On 2011-06-08 03:15, Peng Tao wrote: >> On 6/8/11, Jim Rees wrote: >>> Benny Halevy wrote: >>> >>>   NAK. >>>   This affects all layout types.  In particular it is undesired >>>   for write layouts that extend the file with the objects layout. >>>   The server can extend the layout segments range >>>   over what the client requested so why would the client >>>   ask for artificially large layouts? >>> >>> This has actually been the subject of some debate over Thursday night >>> beers.  The problem we're trying to solve is that the client is spending 98% >>> of its time in layoutget.  This patch gives us something like a 10x >>> speedup.  But many of us think it's not the right fix.  I suggest we discuss >>> next week. >>> > > Sure. > >>> But note that this patch doesn't change anything unless you set the sysctl. >> there is a default value of 2M. maybe we can set it to page size by >> default so other layout are not affected and block layout can let >> users set it by hand if they care about performance. does this make >> sense? > > If doing it at all why use a sysctl rather than a mount option? The purpose of using a sysctl is to give client the ability to change it on the fly. In theory, layout prefetching can benefit all layout types. So the patch tries to solve it in the pnfs generic layer. > Or maybe coding the logic for prefetching the layout iff sequential > access is detected is the right thing to do. Yeah, automatic decision should be a better way. > > Benny > >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at  http://vger.kernel.org/majordomo-info.html >>> >> >> > -- Thanks, -Bergwolf