From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: [PATCH 8/8] IB/srp: Make queue size configurable Date: Fri, 13 Sep 2013 10:40:38 +0200 Message-ID: <5232CF86.20507@acm.org> References: <521363EA.8080906@acm.org> <52136609.3090406@acm.org> <1378782080.3794.6.camel@feather.ornl.gov> <522F5A81.8040101@acm.org> <1378937796.6649.5.camel@haswell.thedillows.org> <5231E8CE.5060105@gmail.com> <5231EC1A.7030902@acm.org> <5232C76B.4010704@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5232C76B.4010704-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jack Wang Cc: David Dillow , David Dillow , Roland Dreier , Vu Pham , Sebastian Riemer , linux-rdma , Konrad Grzybowski List-Id: linux-rdma@vger.kernel.org On 09/13/13 10:06, Jack Wang wrote: > On 09/12/2013 06:30 PM, Bart Van Assche wrote: >> On 09/12/13 18:16, Jack Wang wrote: >>> On 09/12/2013 12:16 AM, David Dillow wrote: >>>> On Tue, 2013-09-10 at 19:44 +0200, Bart Van Assche wrote: >>>>> If this name was not yet in use in any interface that is visible in >>>>> user >>>>> space, I would agree that we should come up with a better name. >>>>> However, >>>>> the SCSI mid-layer already uses that name today to export the queue >>>>> size. To me this looks like a good reason to use the name "can_queue" ? >>>>> An example: >>>>> >>>>> $ cat /sys/class/scsi_host/host93/can_queue >>>>> 62 >>>> >>>> Yes, I know it has been used before, but I'm torn between not furthering >>>> a bad naming choice and consistency. Foolish consistency and all that... >>>> >>>> I really don't like "can_queue", but I'll not complain if Roland decides >>>> to take it as-is. >>> >>> What the allow range for this queue size? >>> Default cmd_per_lun and can_queue with same value makes no sense to me. >>> Could we bump can_queue to bigger value like 512? >> >> Increasing the default value is only necessary when using a hard disk >> array at the target side. When using a single hard disk or an SSD at the >> target side the default value is fine. > > Agree, from another side increasing default can_queue value is harmless > for single harddisk/SSD, but will boot performance for multiple LUN > attached to same host, so why not? Increasing that parameter increases memory consumption for each path between initiator and target. In a setup where both the initiator and the target have multiple IB ports the number of paths can be large even when only a single LUN is exported by the target. That's why I'm not enthusiast about increasing the default value of the queue size. Bart. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html