From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753564Ab0JVIHh (ORCPT ); Fri, 22 Oct 2010 04:07:37 -0400 Received: from mga02.intel.com ([134.134.136.20]:47401 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752952Ab0JVIHb (ORCPT ); Fri, 22 Oct 2010 04:07:31 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.58,222,1286175600"; d="scan'208";a="566407105" Date: Fri, 22 Oct 2010 16:07:25 +0800 From: Wu Fengguang To: Jens Axboe Cc: KOSAKI Motohiro , Torsten Kaiser , Neil Brown , Rik van Riel , Andrew Morton , KAMEZAWA Hiroyuki , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "Li, Shaohua" Subject: Re: Deadlock possibly caused by too_many_isolated. Message-ID: <20101022080725.GA22594@localhost> References: <20101020055717.GA12752@localhost> <20101020150346.1832.A69D9226@jp.fujitsu.com> <20101020092739.GA23869@localhost> <4CBEE888.2090606@kernel.dk> <20101022053755.GB16804@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101022053755.GB16804@localhost> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > We surely need 1 set aside for each level of that stack that will > > potentially consume one. 1 should be enough for the generic pool, and > > then clones will use a separate pool. So md and friends should really > > have a pool per device, so that stacking will always work properly. > > Agreed for the deadlock problem. > > > There should be no throughput concerns, it should purely be a safe guard > > measure to prevent us deadlocking when doing IO for reclaim. > > It's easy to verify whether the minimal size will have negative > impacts on IO throughput. In Torsten's case, increase BIO_POOL_SIZE > by one and check how it performs. Sorry it seems simply increasing BIO_POOL_SIZE is not enough to fix possible deadlocks. We need adding new mempool(s). Because when there BIO_POOL_SIZE=2 and there are two concurrent reclaimers each take 1 reservation, they will deadlock each other when trying to take the next bio at the raid1 level. Thanks, Fengguang From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id BBD066B004A for ; Fri, 22 Oct 2010 04:07:31 -0400 (EDT) Date: Fri, 22 Oct 2010 16:07:25 +0800 From: Wu Fengguang Subject: Re: Deadlock possibly caused by too_many_isolated. Message-ID: <20101022080725.GA22594@localhost> References: <20101020055717.GA12752@localhost> <20101020150346.1832.A69D9226@jp.fujitsu.com> <20101020092739.GA23869@localhost> <4CBEE888.2090606@kernel.dk> <20101022053755.GB16804@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101022053755.GB16804@localhost> Sender: owner-linux-mm@kvack.org To: Jens Axboe Cc: KOSAKI Motohiro , Torsten Kaiser , Neil Brown , Rik van Riel , Andrew Morton , KAMEZAWA Hiroyuki , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "Li, Shaohua" List-ID: > > We surely need 1 set aside for each level of that stack that will > > potentially consume one. 1 should be enough for the generic pool, and > > then clones will use a separate pool. So md and friends should really > > have a pool per device, so that stacking will always work properly. > > Agreed for the deadlock problem. > > > There should be no throughput concerns, it should purely be a safe guard > > measure to prevent us deadlocking when doing IO for reclaim. > > It's easy to verify whether the minimal size will have negative > impacts on IO throughput. In Torsten's case, increase BIO_POOL_SIZE > by one and check how it performs. Sorry it seems simply increasing BIO_POOL_SIZE is not enough to fix possible deadlocks. We need adding new mempool(s). Because when there BIO_POOL_SIZE=2 and there are two concurrent reclaimers each take 1 reservation, they will deadlock each other when trying to take the next bio at the raid1 level. Thanks, Fengguang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org