From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756092Ab1LVWVB (ORCPT ); Thu, 22 Dec 2011 17:21:01 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:44916 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751914Ab1LVWU7 (ORCPT ); Thu, 22 Dec 2011 17:20:59 -0500 Date: Thu, 22 Dec 2011 14:20:58 -0800 From: Andrew Morton To: Tejun Heo Cc: avi@redhat.com, nate@cpanel.net, cl@linux-foundation.org, oleg@redhat.com, axboe@kernel.dk, vgoyal@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCHSET] block, mempool, percpu: implement percpu mempool and fix blkcg percpu alloc deadlock Message-Id: <20111222142058.41316ee0.akpm@linux-foundation.org> In-Reply-To: <20111222220911.GK17084@google.com> References: <1324590326-10135-1-git-send-email-tj@kernel.org> <20111222135925.de3221c8.akpm@linux-foundation.org> <20111222220911.GK17084@google.com> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 22 Dec 2011 14:09:11 -0800 Tejun Heo wrote: > Hello, > > On Thu, Dec 22, 2011 at 01:59:25PM -0800, Andrew Morton wrote: > > How about we just delete those statistics and then this patchset? > > > > Or how about we change those statistics to not do percpu allocations, > > then delete this patchset? > > I'm not against above both Don't just consider my suggestions - please try to come up with your own alternatives too! If all else fails then this patch is a last resort. > but apparently those percpu stats reduced > CPU overhead significantly. Deleting them would save even more CPU. Or make them runtime or compile-time configurable, so only the developers see the impact. Some specifics on which counters are causing the problems would help here. > > Or how about we fix the percpu memory allocation code so that it > > propagates the gfp flags, then delete this patchset? > > Oh, no, this is gonna make things *way* more complex. I tried. But there's a difference between fixing a problem and working around it. > If > we're gonna have many more NOIO percpu users, which I don't think we > would or should, that might make sense but, for fringe cases, > extending mempool to cover percpu is a much better sized solution. I've long felt that we goofed with the gfp_flags thing and that it should be a field in the task_struct. Now *that* would be a large patch!