From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCH] scsi: break from queue depth adjusting loops when device found Date: Fri, 04 Jul 2014 12:53:00 +0200 Message-ID: <53B6878C.502@suse.de> References: <20140703150557.21608.37072.stgit@beardog.cce.hp.com> <20140703171106.GA16788@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from cantor2.suse.de ([195.135.220.15]:51860 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751901AbaGDKxF (ORCPT ); Fri, 4 Jul 2014 06:53:05 -0400 In-Reply-To: <20140703171106.GA16788@lst.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Christoph Hellwig , "Stephen M. Cameron" Cc: james.bottomley@parallels.com, elliott@hp.com, stephenmcameron@gmail.com, linux-scsi@vger.kernel.org, Vasu Dev , Mike Christie On 07/03/2014 07:11 PM, Christoph Hellwig wrote: > On Thu, Jul 03, 2014 at 10:05:57AM -0500, Stephen M. Cameron wrote: >> From: Stephen M. Cameron >> >> Don't loop through all the devices even after >> finding the one we're looking for > > The comments in the code seem to indicate that we want to modify > the queue depth for all LUNs on a given target. > > Ccing Mike and Vasu as they wrote this code. > Indeed, that was the idea. This piece of code tries to keep track of the remote port queue=20 depth, which isn't represented at all. Thing is, each remote target has a target queue depth which can hold=20 only so many outstanding SCSI requests. If that is full it'll return=20 BUSY for _all_ LUNs served from that port. And the very _next_ command after the one which filled the target=20 queue will get the BUSY status. So we need to decrease the queue depth on _all_ LUNs here to avoid=20 starvation of individual devices. Hence I guess this is not the correct fix. Cheers, Hannes --=20 Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: J. Hawn, J. Guild, F. Imend=F6rffer, HRB 16746 (AG N=FCrnberg) -- 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