Date: Wed, 19 Feb 2014 21:59:32 +0200 From: Alexander Motin <mav@FreeBSD.org> To: Adrian Chadd <adrian@freebsd.org> Cc: Jeffrey Faden <jeffreyatw@gmail.com>, freebsd-current <freebsd-current@freebsd.org>, "freebsd-arch@freebsd.org" <freebsd-arch@freebsd.org> Subject: Re: [rfc] bind per-cpu timeout threads to each CPU Message-ID: <53050D24.3020505@FreeBSD.org> In-Reply-To: <CAJ-VmokQ_C=YVpk41_r-QakB46_RWRe0didq1_RrZBMS7hDX-A@mail.gmail.com> References: <530508B7.7060102@FreeBSD.org> <CAJ-VmokQ_C=YVpk41_r-QakB46_RWRe0didq1_RrZBMS7hDX-A@mail.gmail.com>
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On 19.02.2014 21:51, Adrian Chadd wrote: > On 19 February 2014 11:40, Alexander Motin <mav@freebsd.org> wrote: >> Clock interrupt threads, same as other ones are only softly bound to >> specific CPUs by scheduler preferring to run them on CPUs where they are >> scheduled. So far that was enough to balance load, but allowed threads to >> migrate, if needed. Is it too flexible for some use case? > > I saw it migrate under enough CPU load / pressure, right smack bang in > the middle of doing TCP processing. > > 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. -- Alexander Motin
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