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Date: Sat, 31 Jan 2009 11:17:15 +0100 From: Eric Dumazet <dada1@...mosbay.com> To: Evgeniy Polyakov <zbr@...emap.net> CC: Stephen Hemminger <shemminger@...tta.com>, Herbert Xu <herbert@...dor.apana.org.au>, berrange@...hat.com, et-mgmt-tools@...hat.com, davem@...emloft.net, netdev@...r.kernel.org Subject: Re: virt-manager broken by bind(0) in net-next. Evgeniy Polyakov a écrit : > On Sat, Jan 31, 2009 at 10:49:00AM +0100, Eric Dumazet (dada1@...mosbay.com) wrote: >> It appears you are always right, I have nothing to say then. >> >> Stupid I am. >> >> I vote for plain revert of your initial patch, since you are anaware >> of performance problems it introduces. Then, probably nobody cares >> of my complaints, so dont worry. > > Eric, do not get it soo personally :) After all it is only a matter of > how we enjoy the process and have fun with the development. > > Really, I appreciate your work and help, and likely this > misunderstanding happened because of a bad mix of the original bug and > this performance implication. Original bug has really nothing with what > we discuss here. And while the performance problem with bound sockets > creation may be visible, I did not observe it, while the idea > implemented with this approach shows up clearly in the graph I posted. > So I vote by both hands to further improve it by moving things around so > that there would be no unneded cache flushes during update of this > field. > OK OK, as I said, dont worry, it was not a strong feeling from me, only a litle bit upset, thats all. We only need to know if the *fix* is solving Stephen problem About performance effects of careful variable placement and percpu counter strategy you might consult as an example : http://lkml.indiana.edu/hypermail/linux/kernel/0812.1/01624.html Now, with these patches applied, try to see effect of your new bsockets field on a network workload doing lot of socket bind()/unbind() calls... With current kernels, you probably wont notice because of inode/dcache hot cache lines, but it might change eventually... -- 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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