From: Ingo Molnar <mingo@elte.hu>
To: Don Zickus <dzickus@redhat.com>
Cc: peterz@infradead.org, gorcunov@gmail.com, fweisbec@gmail.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] [lockup detector] sync touch_*_watchdog back to old semantics
Date: Wed, 1 Sep 2010 07:30:55 +0200 [thread overview]
Message-ID: <20100901053055.GA14316@elte.hu> (raw)
In-Reply-To: <1283310009-22168-2-git-send-email-dzickus@redhat.com>
* Don Zickus <dzickus@redhat.com> wrote:
> void touch_nmi_watchdog(void)
> {
> - __get_cpu_var(watchdog_nmi_touch) = true;
> + if (watchdog_enabled) {
> + unsigned cpu;
> +
> + for_each_present_cpu(cpu) {
> + if (per_cpu(watchdog_nmi_touch, cpu) != true)
> + per_cpu(watchdog_nmi_touch, cpu) = true;
> + }
Hm, this is going to be a scalability nightmare with lots of CPUs. Not
only do we have a nr_cpus loop, but we touch per-cpu areas of _other_
CPUs - a big scalability nono.
Why do we need to do this? We never needed to touch other CPU's NMI
lockup accounting data areas - why has this changed? The changelog does
not explain this.
Thanks,
Ingo
next prev parent reply other threads:[~2010-09-01 5:31 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-01 3:00 [PATCH 0/3] lockup detector fixes Don Zickus
2010-09-01 3:00 ` [PATCH 1/3] [lockup detector] sync touch_*_watchdog back to old semantics Don Zickus
2010-09-01 5:30 ` Ingo Molnar [this message]
2010-09-01 6:00 ` Cyrill Gorcunov
2010-09-01 7:01 ` Cyrill Gorcunov
2010-09-01 7:20 ` Ingo Molnar
2010-09-01 7:42 ` Cyrill Gorcunov
2010-09-01 9:19 ` [tip:perf/urgent] lockup_detector: Sync " tip-bot for Don Zickus
2010-09-01 3:00 ` [PATCH 2/3] lockup_detector: convert cpu notifier to return encapsulate errno value Don Zickus
2010-09-01 6:24 ` [tip:perf/core] lockup_detector: Convert " tip-bot for Akinobu Mita
2010-09-01 3:00 ` [PATCH 3/3] lockup_detector: remove unnecessary panic_notifier Don Zickus
2010-09-01 6:25 ` [tip:perf/core] lockup_detector: Remove unused panic_notifier tip-bot for Akinobu Mita
-- strict thread matches above, loose matches on Subject: below --
2010-09-01 15:51 [PATCH 1/3] [lockup detector] sync touch_*_watchdog back to old semantics Don Zickus
2010-09-01 16:36 ` Cyrill Gorcunov
2010-09-01 17:15 ` Ingo Molnar
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