From: Ingo Molnar <mingo@elte.hu>
To: Arjan van de Ven <arjan@infradead.org>
Cc: linux-kernel@vger.kernel.org, Milton Miller <miltonm@bga.com>,
Andrew Morton <akpm@linux-foundation.org>,
arjanvandeven@gmail.com,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: smp: Start up non-boot CPUs asynchronously
Date: Tue, 31 Jan 2012 15:31:31 +0100 [thread overview]
Message-ID: <20120131143130.GF13676@elte.hu> (raw)
In-Reply-To: <20120131054155.371e8307@infradead.org>
* Arjan van de Ven <arjan@infradead.org> wrote:
> On Tue, 31 Jan 2012 13:52:32 +0100
> Ingo Molnar <mingo@elte.hu> wrote:
> >
> > The real fix would be to make the init code depend less on each
> > other, i.e. have less hotplug lock dependencies. Or, if it's
> > such a hot lock for a good reason, why does spinning on it slow
> > down the boot process? It really shouldnt.
>
> by inspection, anything that calls
> get_online_cpus()/put_online_cpus() will block while a CPU is
> coming up. This is used in things like kmem_cache_create()...
> which is used about everywhere. (there's various other
> places... more or less it's a requirement for using the
> for_each_online_cpu() api correctly)
Still magic delays are not acceptable - we want to face any
remaining performance problems head on, we want to understand
and fix them correctly.
Thanks,
Ingo
next prev parent reply other threads:[~2012-01-31 14:31 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-31 4:54 smp: Start up non-boot CPUs asynchronously Arjan van de Ven
2012-01-31 12:52 ` Ingo Molnar
2012-01-31 13:41 ` Arjan van de Ven
2012-01-31 14:31 ` Ingo Molnar [this message]
2012-01-31 15:22 ` Arjan van de Ven
2012-01-31 16:12 ` Ingo Molnar
2012-01-31 16:24 ` Arjan van de Ven
2012-02-01 22:55 ` Andrew Morton
[not found] ` <CADyApD0yVOePmaLznks_h6xR_BCUjzEFUB7VtsL9vvsoHwCOVw@mail.gmail.com>
2012-02-01 23:31 ` Linus Torvalds
2012-02-14 8:17 ` Srivatsa S. Bhat
2012-02-14 9:48 ` Srivatsa S. Bhat
2012-02-14 19:32 ` Srivatsa S. Bhat
[not found] ` <CADyApD0o4UYsTkqf2H2yJZ-d05NAyRAEc6z+m1gJEogc=cZLqQ@mail.gmail.com>
2012-02-14 15:20 ` Peter Zijlstra
2012-02-14 19:57 ` Srivatsa S. Bhat
2012-02-14 20:00 ` Peter Zijlstra
2012-02-14 21:02 ` Arjan van de Ven
2012-02-14 21:28 ` Benjamin Herrenschmidt
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