linux-kernel - Re: [RFC/RFT PATCH] sched: automated per tty task groups

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20101020025652.GB26822@elte.hu>
Date:	Wed, 20 Oct 2010 04:56:52 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Mike Galbraith <efault@....de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [RFC/RFT PATCH] sched: automated per tty task groups

* Mike Galbraith <efault@....de> wrote:

> > On Tue, 2010-10-19 at 08:28 -0700, Linus Torvalds wrote:
> > >
> > >  If people compare with a non-CGROUP_SCHED
> > > kernel, will a desktop-optimized kernel suddenly have horrible pipe
> > > latency due to much higher scheduling cost? Right now that whole
> > > feature is hidden by EXPERIMENTAL, I don't know how much it hurts, and
> > > I never timed it when I tried it out long ago..
> 
> Q/D test of kernels w/wo, with same .config using pipe-test (pure sched) gives on 
> my box ~590khz with tty_sched active, 620khz without cgroups acitve in same 
> kernel/config without patch.  last time I measured stripped down config (not long 
> ago, but not yesterday either) gave max ctx rate ~690khz on this box.
> 
> (note: very Q, very D numbers, no variance testing, ballpark)

That's 5% overhead in context switches. Definitely not in the 'horrible' category.

This would be a rather tempting item for 2.6.37 ... especially as it really mainly 
reuses existing group scheduling functionality, in a clever way.

Mind doing more of the tty->desktop renames/generalizations as Linus suggested, and 
resend the patch?

I'd also suggest to move it out of EXPERIMENTAL - we dont really do that for core 
kernel features as most distros enable CONFIG_EXPERIMENTAL so it's a rather 
meaningless distinction. Since the feature is default-n, people will get the old 
scheduler by default but can also choose this desktop-centric scheduling mode.

I'd even argue to make it default-y, because this patch clearly cures a form of 
kbuild cancer.

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/