Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423397AbbEOXaj (ORCPT ); Fri, 15 May 2015 19:30:39 -0400 Received: from cantor2.suse.de ([195.135.220.15]:55273 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423017AbbEOXae (ORCPT ); Fri, 15 May 2015 19:30:34 -0400 Date: Sat, 16 May 2015 09:30:22 +1000 From: NeilBrown To: Andreas Dilger Cc: Dave Chinner , Linus Torvalds , Al Viro , Linux Kernel Mailing List , linux-fsdevel , Christoph Hellwig Subject: Re: [RFC][PATCHSET v3] non-recursive pathname resolution & RCU symlinks Message-ID: <20150516093022.51e1464e@notabene.brown> In-Reply-To: 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> X-Mailer: Claws Mail 3.10.1-162-g4d0ed6 (GTK+ 2.24.25; x86_64-suse-linux-gnu) MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; boundary="Sig_/uu6RstifEhvEGDjyEYZ0WJj"; protocol="application/pgp-signature" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3475 Lines: 82 --Sig_/uu6RstifEhvEGDjyEYZ0WJj Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Fri, 15 May 2015 15:15:48 -0600 Andreas Dilger wrote: > On May 14, 2015, at 5:23 AM, Dave Chinner wrote: > >=20 > > On Wed, May 13, 2015 at 08:52:59PM -0700, Linus Torvalds wrote: > >> On Wed, May 13, 2015 at 8:30 PM, Al Viro wro= te: > >>>=20 > >>> Maybe... I'd like to see the profiles, TBH - especially getxattr() a= nd > >>> 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... > >>=20 > >> So I haven't seen samba profiles in ages, but iirc we have more > >> serious problems than trying to speed up basic filename lookup. > >>=20 > >> At least long long ago, inode semaphore contention was a big deal, > >> largely due to readdir(). > >=20 > > 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.... >=20 > 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 blo= ck > 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). .. and I've been wondering what to do about i_mutex and NFS. I've had customer reports of slowness in creating files that seems to be due to i_mutex on the directory being held over the whole 'create' RPC, so only one of those can be in flight at the one time. "make -j" on a large source directory can easily want to create lots of "*.o" files at "the same time". And NFS doesn't need i_mutex at all because the server will provide the needed guarantees. NeilBrown --Sig_/uu6RstifEhvEGDjyEYZ0WJj Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIVAwUBVVaBjjnsnt1WYoG5AQLtIhAAkvEjdB+6OtoWxihQ1av7OiGNnOWesuYM Qo+x93CtuP4NMh55GDTbAc2yL/2mTAiI4fKDa/GnE42LUeQs+K95wwx8jL0P/iij BZDRN1c52x97wzQgPq1rQKfzknJAUOn4lPdbSQD4zhZpTlquro17NlZyEPUasapP //w5lP1WlZgpZznb6h3PVdNxCR/chTf3XMbuMgZhtkS9m4A8E/4SyDvLjSl/7Qs9 pb4YarCF7RLiJJNnVbEyZgO2TGfjmld89azhWsxk/s3yALigqIulYVBB+B6jW4bc cIQnVs/4fEFEsOPkrjV92V2J7SGdt4142GiR+65cOLVC0Ax7MUmR6dkkEoP7tsiw y1nYblW6sfJELpesyCx0fs/sEUn7isTvyDepHWkgjnTOuGCYD5D9fA0+NBpx/v/m 60pu51IYKQjEZ7VvfS143WKTCv17dXUraR1ZucLAR+/5dz8czLOlJFD5VwRPZBsa aXBkQiFo9Xf9EyVfhpB8SkJjkezgHVaO26OAAiNHon48hYFUMxY+4so+4vH+qFok WhH0S1+W07+TAZVUnL2OYB9rPB6u6VL3epoUu7gXfApYPNud+dMaGCpTYg+iHN6Q UxSga1NiAcU70hKh6Lcxqw96/mOFT8p9YDiPi6MQ/jkiatJJV4O6rw7ms02a7cbp 3BhT1ZRd3P0= =/FQS -----END PGP SIGNATURE----- --Sig_/uu6RstifEhvEGDjyEYZ0WJj-- -- 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/