Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751474AbaEADMz (ORCPT ); Wed, 30 Apr 2014 23:12:55 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:49767 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750848AbaEADMy (ORCPT ); Wed, 30 Apr 2014 23:12:54 -0400 Date: Thu, 1 May 2014 04:12:51 +0100 From: Al Viro To: Linus Torvalds Cc: Miklos Szeredi , Dave Chinner , Linux Kernel Mailing List , linux-fsdevel Subject: Re: dcache shrink list corruption? Message-ID: <20140501031251.GZ18016@ZenIV.linux.org.uk> References: <20140430203823.GT18016@ZenIV.linux.org.uk> <20140430211206.GU18016@ZenIV.linux.org.uk> <20140430221238.GV18016@ZenIV.linux.org.uk> <20140430234341.GX18016@ZenIV.linux.org.uk> <20140501025105.GY18016@ZenIV.linux.org.uk> 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 On Wed, Apr 30, 2014 at 07:59:43PM -0700, Linus Torvalds wrote: > On Wed, Apr 30, 2014 at 7:51 PM, Al Viro wrote: > > > > Help with profiling is needed; the loads to watch are > > the ones where dentry_kill() + dentry_free() are sufficiently high in profiles > > for the differences to matter. Any takers? > > I really hope there are no such loads, my "lock/unlock pairing" > suggestion was mostly so that the pairing is clearer, not necessarily > for performance. > > That said, I'd assume that it migth be worth testing at least the > "lots of concurrent lookups of 'simple_dentry_operations' dentries". > So most of /proc, most uses of simple_lookup(). That at least triggers > the dentry_kill() path in dput(), so it should be fairly easy to get > profiles. > > But real loads with real filesystems? That sounds harder. Well, the simplest way to do that is a bunch of open/unlink/close. Another one is cp -rl / rm -rf of a large tree (rmdir(2) does shrink_dcache_parent()). For that matter, unmapping an anon shared mapping will trigger the same path. -- 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/