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Message-Id: <1190034238.4230.113.camel@localhost> Date: Mon, 17 Sep 2007 09:03:58 -0400 From: jamal <hadi@...erus.ca> To: Evgeniy Polyakov <johnpol@....mipt.ru> Cc: David Miller <davem@...emloft.net>, herbert@...dor.apana.org.au, netdev@...r.kernel.org, kaber@...sh.net, dada1@...mosbay.com Subject: Re: [RFC][NET_SCHED] explict hold dev tx lock On Mon, 2007-17-09 at 14:27 +0400, Evgeniy Polyakov wrote: > > How many cpu collisions you are seeing? On 4 CPUs which were always transmitting very few - there was contention in the range of 100 per million attempts. Note: it doesnt matter that 4 cpus were busy, this lock is contended at max (for all NAPI drivers i poked into) between two CPUs. > Did I understand you right, that you replaced trylock with lock and > thus removed collision handling and got better results? Yes, a small one with the 4 CPUs and no irq binding. Note that in the test cases i run, the contention for queue lock was high (since all CPUs were busy processing traffic). I think as the the number of CPUs go up, this will become more prominent. The choice is between contending for queue lock or this lock. One lock is contended by max of two cpus, the other by N cpus. As N goes up, you want to have more mercy on the one that is contended by N cpus. Did that make sense? cheers, jamal - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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