Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2993118AbbEOXjU (ORCPT ); Fri, 15 May 2015 19:39:20 -0400 Received: from ipmail06.adl6.internode.on.net ([150.101.137.145]:2243 "EHLO ipmail06.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2992469AbbEOXjQ (ORCPT ); Fri, 15 May 2015 19:39:16 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: A2BiBwD1glZVPPDOLHlcgxBUXrJjAQEBAQaZSwICAQECgSxNAQEBAQEBBwEBAQFBP4QjAQEEOhwjEAgDDgoJJQ8FJQMHGhOIK9c+AQEIAgEfGIV+hSSFBQeELQWdU5cAgQSDKSwxgkYBAQE Date: Sat, 16 May 2015 09:39:13 +1000 From: Dave Chinner To: Andreas Dilger Cc: Linus Torvalds , Al Viro , Linux Kernel Mailing List , linux-fsdevel , Christoph Hellwig , Neil Brown Subject: Re: [RFC][PATCHSET v3] non-recursive pathname resolution & RCU symlinks Message-ID: <20150515233913.GI4316@dastard> References: <20150505052205.GS889@ZenIV.linux.org.uk> <20150511180650.GA4147@ZenIV.linux.org.uk> <20150513222533.GA24192@ZenIV.linux.org.uk> <20150514033040.GF7232@ZenIV.linux.org.uk> <20150514112304.GT15721@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2007 Lines: 44 On Fri, May 15, 2015 at 03:15:48PM -0600, Andreas Dilger wrote: > On May 14, 2015, at 5:23 AM, Dave Chinner wrote: > > > > On Wed, May 13, 2015 at 08:52:59PM -0700, Linus Torvalds wrote: > >> On Wed, May 13, 2015 at 8:30 PM, Al Viro wrote: > >>> > >>> Maybe... I'd like to see the profiles, TBH - especially getxattr() and > >>> access() frequency on various loads. Sure, make(1) and cc(1) really care > >>> about stat() very much, but I wouldn't be surprised if something like > >>> httpd or samba would be hitting getxattr() a lot... > >> > >> So I haven't seen samba profiles in ages, but iirc we have more > >> serious problems than trying to speed up basic filename lookup. > >> > >> At least long long ago, inode semaphore contention was a big deal, > >> largely due to readdir(). > > > > It still is - it's the prime reason people still need to create > > hashed directory structures so that they can get concurrency in > > directory operations. IMO, concurrency in directory operations is a > > more important problem to solve than worrying about readdir speed; > > in large filesystems readdir and lookup are IO bound operations and > > so everything serialises on the IO as it's done with the i_mutex > > held.... > > We've had a patch[*] to add ext4 parallel directory operations in Lustre for > a few years, that adds separate locks for each internal tree and leaf block > instead of using i_mutex, so it scales as the size of the directory grows. > This definitely improved many-threaded directory create/lookup/unlink > performance (rename still uses a single lock). Yup, we can do the same to XFS to implement concurrent modifications. Cheers, Dave. -- Dave Chinner david@fromorbit.com -- 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/