From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Bolkhovitin Subject: Re: SRP initiator and iSER initiator performance Date: Wed, 03 Mar 2010 23:23:05 +0300 Message-ID: <4B8EC529.9010202@vlnb.net> References: <4B8C1FBF.8060001@vlnb.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Bart Van Assche Cc: Chris Worley , David Dillow , OFED mailing list , scst-devel List-Id: linux-rdma@vger.kernel.org Bart Van Assche, on 03/02/2010 09:59 AM wrote: > On Mon, Mar 1, 2010 at 9:12 PM, Vladislav Bolkhovitin wrote: >> [ ... ] >> It's good if my impression was wrong. But you've got suspiciously low IOPS >> numbers. On your hardware you should have much more. Seems you experienced a >> bottleneck on the initiator somewhere above the drivers level (fio? sg >> engine? IRQs or context switches count?), so your results could be not >> really related to the topic. Oprofile and lockstat output can shed more >> light on this. > > You didn't understand the purpose of the test. My goal was not to > achieve record IOPS numbers but to stress the SRP and iSER initiators > as much as possible. I choose the sg I/O engine in order to bypass the > block layer. No, Bart, I understood your purpose very well. I'll illustrate my point on example. Let's consider we want to compare a Ferrari and Toyota Corolla cars. The only track we have to use has 60km/h speed limit, so we used it strictly following the speed limit. Would we have a correct comparison of the cars' capabilities, or would we compare only their speedometers' mistakes? If Toyota's speedometer allows to stay more closely to the limit, Toyota can win Ferrari. But would it win too on 180 km/h limit? Or without speed limit at all? The same is in our topic. We can consider your experiment correct only if the bottleneck is driver/hardware, which isn't likely to be. Vlad -- 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