On 2/19/14, 12:04 PM, Adrian Chadd wrote: > On 19 February 2014 11:59, Alexander Motin <mav_at_freebsd.org> wrote: > >>> So if we're moving towards supporting (among others) a pcbgroup / RSS >>> hash style work load distribution across CPUs to minimise >>> per-connection lock contention, we really don't want the scheduler to >>> decide it can schedule things on other CPUs under enough pressure. >>> That'll just make things worse. >> True, though it is also not obvious that putting second thread on CPU run >> queue is better then executing it right now on another core. > Well, it depends if you're trying to optimise for "run all runnable > tasks as quickly as possible" or "run all runnable tasks in contexts > that minimise lock contention." > > The former sounds great as long as there's no real lock contention > going on. But as you add more chances for contention (something like > "100,000 concurrent TCP flows") then you may end up having your TCP > timer firing stuff interfere with more TXing or RXing on the same > connection. > > Chasing this stuff down is a pain, because it only really shows up > when you're doing lots of concurrency. > > I'm happy to make this a boot-time option and leave it off for the > time being. How's that? options THROUGHPUT Yes, looks like a latency vs throughput issue. One giant switch might be a starting point so that it doesn't become death of 1000 switches to get throughput or latency sensitive work done. > > > > -a > _______________________________________________ > freebsd-current_at_freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org" >Received on Wed Feb 19 2014 - 19:32:17 UTC
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