Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755515Ab0F1Wcq (ORCPT ); Mon, 28 Jun 2010 18:32:46 -0400 Received: from mail-gy0-f174.google.com ([209.85.160.174]:33102 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753901Ab0F1Wcp (ORCPT ); Mon, 28 Jun 2010 18:32:45 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; b=RhK6FR4ICkq5H698DZURc/5FGSIYFkDE0xXb4LPIe6qmGnFpMHr5xtr8AClRGNu91j Rvn7lz3SL1jNQc1+Nsx/Vk4hETB86A6VI2QHSc41ARwVs+cPe5wtiq5a2oCbVv2DOJ1B OKeB67AmSrYp4ElA+klQzkJolEtwTfXlcy9bY= Message-ID: <4C292308.4050906@pobox.com> Date: Mon, 28 Jun 2010 18:32:40 -0400 From: Jeff Garzik User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100430 Fedora/3.0.4-2.fc12 Thunderbird/3.0.4 MIME-Version: 1.0 To: Tejun Heo CC: torvalds@linux-foundation.org, mingo@elte.hu, linux-kernel@vger.kernel.org, jeff@garzik.org, akpm@linux-foundation.org, rusty@rustcorp.com.au, cl@linux-foundation.org, dhowells@redhat.com, arjan@linux.intel.com, oleg@redhat.com, axboe@kernel.dk, fweisbec@gmail.com, dwalker@codeaurora.org, stefanr@s5r6.in-berlin.de, florian@mickler.org, andi@firstfloor.org, mst@redhat.com, randy.dunlap@oracle.com Subject: Re: [PATCH 33/35] libata: take advantage of cmwq and remove concurrency limitations References: <1277759063-24607-1-git-send-email-tj@kernel.org> <1277759063-24607-34-git-send-email-tj@kernel.org> In-Reply-To: <1277759063-24607-34-git-send-email-tj@kernel.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1153 Lines: 29 On 06/28/2010 05:04 PM, Tejun Heo wrote: > libata has two concurrency related limitations. > > a. ata_wq which is used for polling PIO has single thread per CPU. If > there are multiple devices doing polling PIO on the same CPU, they > can't be executed simultaneously. > > b. ata_aux_wq which is used for SCSI probing has single thread. In > cases where SCSI probing is stalled for extended period of time > which is possible for ATAPI devices, this will stall all probing. > > #a is solved by increasing maximum concurrency of ata_wq. Please note > that polling PIO might be used under allocation path and thus needs to > be served by a separate wq with a rescuer. > > #b is solved by using the default wq instead and achieving exclusion > via per-port mutex. > > Signed-off-by: Tejun Heo > Cc: Jeff Garzik Acked-by: Jeff Garzik -- 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/