From: Arjan van de Ven <arjan@infradead.org>
To: Ingo Molnar <mingo@elte.hu>
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 07:22:16 -0800 [thread overview]
Message-ID: <20120131072216.1ce78e50@infradead.org> (raw)
In-Reply-To: <20120131143130.GF13676@elte.hu>
On Tue, 31 Jan 2012 15:31:31 +0100
Ingo Molnar <mingo@elte.hu> wrote:
> >
> > 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.
it's not really a performance problem as it is an obvious "we have a
ton of back-to-back writers on a read-write lock that we have quite a
few readers for". Unless the writers back off a little, the readers are
going to get starved.
--
Arjan van de Ven Intel Open Source Technology Centre
For development, discussion and tips for power savings,
visit http://www.lesswatts.org
next prev parent reply other threads:[~2012-01-31 15:20 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-31 4:54 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
2012-01-31 15:22 ` Arjan van de Ven [this message]
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
[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 19:32 ` Srivatsa S. Bhat
2012-02-14 21:28 ` Benjamin Herrenschmidt
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