Date: Thu, 22 Jan 2015 01:00:44 +1100 From: Lawrence Stewart <lstewart@freebsd.org> To: Adrian Chadd <adrian@freebsd.org>, Hans Petter Selasky <hselasky@freebsd.org> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org> Subject: Re: svn commit: r277213 - in head: share/man/man9 sys/kern sys/ofed/include/linux sys/sys Message-ID: <54BFB10C.9080004@freebsd.org> In-Reply-To: <CAJ-VmomOE6AzbEFw45VOtVbLTtDMbnixkYDVK951pSCkcMrQjQ@mail.gmail.com> References: <201501151532.t0FFWV2Y037455@svn.freebsd.org> <CAJ-Vmok0GXZoojyi=jE=b5D-d338APztaf3Pw0_AAQ-173XSWw@mail.gmail.com> <CAJ-VmomOE6AzbEFw45VOtVbLTtDMbnixkYDVK951pSCkcMrQjQ@mail.gmail.com>
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On 01/20/15 09:22, Adrian Chadd wrote: > Yeah, it looks like you set c_cpu to timeout_cpu in > _callout_init_locked(), but then you only handle the case of the CPU > being changed in certain circumstances. You aren't handling the CPU > being initialised when the callout is first added. > > And, callout_restart_async() calls callout_lock(), which calls > CC_LOCK() on the callout CPU, which initially is zero. Then, it never > seems to be 'moved' into the correct CPU, even though it's being > called with a CPU id. > > So, if I am reading this all correctly, you aren't really handling > multi CPU callwheels at all. ;) > > In my instance, I'm seeing quite a lot of lock contention between the > userland threads, the network RX threads and the clock thread, all > contending on a single callout wheel being used for TCP timers. One of > the early goals for fixing up the RSS stuff in -HEAD was to make > per-CPU (Well, per-RSS-bucket really) TCP timers not contend with the > NIC RX processing path, and now it does. :( To clarify, you're seeing this with net.inet.tcp.per_cpu_timers=1? Cheers, Lawrence
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