From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [PATCH v1 0/8] Deferred dput() and iput() -- reducing lock contention Date: Wed, 21 Jan 2009 06:52:16 +0100 Message-ID: <877i4pdx4f.fsf@basil.nowhere.org> References: <20090117022936.20425.43248.stgit@crlf.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Mike Waychison Return-path: Received: from one.firstfloor.org ([213.235.205.2]:43225 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751124AbZAUFxJ (ORCPT ); Wed, 21 Jan 2009 00:53:09 -0500 In-Reply-To: <20090117022936.20425.43248.stgit@crlf.corp.google.com> (Mike Waychison's message of "Fri, 16 Jan 2009 18:29:36 -0800") Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Mike Waychison writes: > livelock on dcache_lock/inode_lock (specifically in atomic_dec_and_lock()) I'm not sure how something can livelock in atomic_dec_and_lock which doesn't take a spinlock itself? Are you saying you run into NUMA memory unfairness here? Or did I misparse you? > This patchset is an attempt to try and reduce the locking overheads associated > with final dput() and final iput(). This is done by batching dentries and > inodes into per-process queues and processing them in 'parallel' to consolidate > some of the locking. I was wondering what this does to the latencies when dput/iput is only done for very objects. Does it increase costs then significantly? As a high level comment it seems like a lot of work to work around global locks, like the inode_lock, where it might be better to just split the lock up? Mind you I don't have a clear proposal how to do that, but surely it's doable somehow. -Andi -- ak@linux.intel.com -- Speaking for myself only.