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Date: Fri, 12 Sep 2008 10:58:37 -0400 From: Elad Lahav <elahav@...terloo.ca> To: "Brandeburg, Jesse" <jesse.brandeburg@...el.com> CC: Elad Lahav <elad_lahav@...rs.sourceforge.net>, e1000-devel@...ts.sourceforge.net, netdev@...r.kernel.org Subject: Re: [E1000-devel] Performance degradration 2.6.25->2.6.26 >> HyperThreading, for a total of 4 logical processors, and 4 Intel Gigabit >> NICs on a PCI 64/66 bus (82546EB). In the experiments, I am pinning >> four sending processes (one per NIC) to logical processors 0 and 2, and >> the NIC interrupts to logical processors 1 and 3, such that interrupts >> are serviced by the sibling logical processor of the one sending the >> packets. I have used both the driver that comes with the Linux kernel >> (7.3.20-k2-NAPI), as well as a more recent one (7.6.15.5). I believe I have found the problem, and it has nothing to do with the driver. Up to the latest kernel, logical processors on the same chip had sequential CPU IDs. So CPU 0 and CPU 1 were two logical processors on the first physical one, 2 and 3 on the second physical one, etc. It seems that now this ordering has changed. I was running my experiments on logical processors 0 and 2, assuming they were on different physical processors, when, in fact, they were sharing the same one. When pinning the processes to logical processor 0 and 1, I get at least as good a performance as I do on previous kernels. Thanks, Elad -- 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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