From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: scsi-mq performance check Date: Fri, 18 Dec 2015 16:08:24 +0100 Message-ID: <56742168.6030200@suse.de> References: <56741F04.3070506@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mx2.suse.de ([195.135.220.15]:35396 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751925AbbLRPI0 (ORCPT ); Fri, 18 Dec 2015 10:08:26 -0500 In-Reply-To: <56741F04.3070506@huawei.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: John Garry , bart.vanassche@sandisk.com, hch@infradead.org, "linux-scsi@vger.kernel.org" On 12/18/2015 03:58 PM, John Garry wrote: > Hi, > > I have started to enable scsi-mq on the HiSilicon SAS driver. > > Are there hints/checks I should use to make sure it is configured > correctly/optimally? In my initial testing I have seen some > performance improvements, but none like what I have seen in > presentations. > The whole thing is build around having symmetric submit and receive=20 queues, so that we can tack a send/receive queue pair to the same=20 CPU. With that we can ensure that we don't have any cache=20 invalidation, as the request is already in the cache for that CPU=20 when the completion is recieved. _And_ we can get rid of most=20 spinlocks as other CPUs cannot access our request. So make sure to have the submit and receive queues properly done,=20 and ensure you don't have any global resources within your driver=20 which needs to be locked. Or move access to those resources out of=20 the fast path. Cheers, Hannes --=20 Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N=C3=BCrnberg GF: F. Imend=C3=B6rffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG N=C3=BCrnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html