Date: Wed, 4 Jun 2014 11:06:11 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-hackers@freebsd.org Cc: Konstantin Belousov <kostikbel@gmail.com>, hackers@freebsd.org, "Alexander V. Chernikov" <melifaro@freebsd.org> Subject: Re: Permit init(8) use its own cpuset group. Message-ID: <201406041106.11659.jhb@freebsd.org> In-Reply-To: <20140602164850.GS3991@kib.kiev.ua> References: <538C8F9A.4020301@FreeBSD.org> <20140602164850.GS3991@kib.kiev.ua>
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On Monday, June 02, 2014 12:48:50 pm Konstantin Belousov wrote:
> On Mon, Jun 02, 2014 at 06:52:10PM +0400, Alexander V. Chernikov wrote:
> > Hello list!
> >
> > Currently init(8) uses group 1 which is root group.
> > Modifications of this group affects both kernel and userland threads.
> > Additionally, such modifications are impossible, for example, in presence
> > of multi-queue NIC drivers (like igb or ixgbe) which binds their threads
to
> > particular cpus.
> >
> > Proposed change ("init_cpuset" loader tunable) permits changing cpu
> > masks for
> > userland more easily. Restricting user processes to migrate to/from CPU
> > cores
> > used for network traffic processing is one of the cases.
> >
> > Phabricator: https://phabric.freebsd.org/D141 (the same version attached
> > inline)
> >
> > If there are no objections, I'll commit this next week.
> Why is the tunable needed ?
Because some people already depend on doing 'cpuset -l 0 -s 1'. It is also
documented in our manpages that processes start in cpuset 1 by default so
that you can use 'cpuset -l 0 -s 1' to move all processes, etc.
For the stated problem (bound ithreads in drivers), I would actually like to
fix ithreads that are bound to a specific CPU to create a different cpuset
instead so they don't conflict with set 1.
--
John Baldwin
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