From: Jeremy Fitzhardinge <jeremy@goop.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Should irq_chip->mask disable percpu interrupts to all cpus, or just to this cpu?
Date: Wed, 24 Sep 2008 11:33:42 -0700 [thread overview]
Message-ID: <48DA8806.4060405@goop.org> (raw)
In-Reply-To: <m18wthna2f.fsf@frodo.ebiederm.org>
Eric W. Biederman wrote:
> I really hate the notion of sharing a single irq_desc across
> multiple cpus as a preferred mode of operation. As NUMA comes
> into play it guarantees we will have cross cpu memory fetches
> on a fast path for irq handling.
>
> Other than the beautiful way we print things in /proc/interrupts
> IRQ_PER_CPU feels like a really bad idea. Especially in that
> it enshrines the nasty per cpu irq counters that scale horribly.
>
I found handle_percpu_irq() which addresses my concerns. It doesn't
attempt to mask the interrupt, takes no locks, and doesn't set or test
IRQ_INPROGRESS in desc->status, so it will scale perfectly across
multiple cpus. It makes no changes to the desc structure, so there
isn't even any cacheline bouncing.
J
next prev parent reply other threads:[~2008-09-24 18:33 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-23 20:02 Should irq_chip->mask disable percpu interrupts to all cpus, or just to this cpu? Jeremy Fitzhardinge
2008-09-24 8:45 ` Ingo Molnar
2008-09-24 9:54 ` Eric W. Biederman
2008-09-24 10:18 ` Ingo Molnar
2008-09-24 18:33 ` Jeremy Fitzhardinge [this message]
2008-09-24 19:34 ` Eric W. Biederman
2008-09-27 19:44 ` Ingo Molnar
2008-09-28 4:58 ` Jeremy Fitzhardinge
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