Date: Tue, 20 Jan 2015 11:00:57 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Hans Petter Selasky <hps@selasky.org> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, Adrian Chadd <adrian@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org> Subject: Re: svn commit: r277213 - in head: share/man/man9 sys/kern sys/ofed/include/linux sys/sys Message-ID: <20150120090057.GD42409@kib.kiev.ua> In-Reply-To: <54BE0AAA.4050104@selasky.org> References: <201501151532.t0FFWV2Y037455@svn.freebsd.org> <CAJ-Vmok0GXZoojyi=jE=b5D-d338APztaf3Pw0_AAQ-173XSWw@mail.gmail.com> <54BDD9E1.6090505@selasky.org> <20150120075126.GA42409@kib.kiev.ua> <54BE0AAA.4050104@selasky.org>
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On Tue, Jan 20, 2015 at 08:58:34AM +0100, Hans Petter Selasky wrote:
> On 01/20/15 08:51, Konstantin Belousov wrote:
> > On Tue, Jan 20, 2015 at 05:30:25AM +0100, Hans Petter Selasky wrote:
> >> On 01/19/15 22:59, Adrian Chadd wrote:
> >>> Hi,
> >>>
> >>> Would you please check what the results of this are with CPU specific
> >>> callwheels?
> >>>
> >>> I'm doing some 10+ gig traffic testing on -HEAD with RSS enabled (on
> >>> ixgbe) and with this setup, the per-CPU TCP callwheel stuff is
> >>> enabled. But all the callwheels are now back on clock(0) and so is the
> >>> lock contention. :(
> >>>
> >>> Thanks,
> >>>
> >>
> >> Hi,
> >>
> >> Like stated in the manual page, callout_reset_curcpu/on() does not work
> >> with MPSAFE callouts any more!
> > I.e. you 'fixed' some undeterminate bugs in callout migration by not
> > doing migration at all anymore.
> >
> >>
> >> You need to use callout_init_{mtx,rm,rw} and remove the custom locking
> >> inside the callback in the TCP stack to get it working like before!
> >
> > No, you need to do this, if you think that whole callout KPI must be
> > rototiled. It is up to the person who modifies the KPI, to ensure that
> > existing code is not broken.
> >
> > As I understand, currently we are back to the one-cpu callouts.
> > Do other people consider this situation acceptable ?
> >
>
> Hi Konstantin,
>
> Please read the callout 9 manual page first.
Assume I read it. How this changes any of my points above ?
"""
A change in the CPU selection cannot happen if this function is
re-scheduled inside a callout function. Else the callback function given
by the func argument will be executed on the same CPU like previously
done.
"""
You cannot do this without fixing consumers.
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