From: Andi Kleen <andi@firstfloor.org>
To: David Miller <davem@davemloft.net>
Cc: andi@firstfloor.org, linux-kernel@vger.kernel.org
Subject: Re: x86's nmi_hz wrt. oprofile's nmi_timer_int.c
Date: Mon, 23 Feb 2009 07:34:07 +0100 [thread overview]
Message-ID: <20090223063406.GS26292@one.firstfloor.org> (raw)
In-Reply-To: <20090222.215906.240407314.davem@davemloft.net>
> Look at the fallback logic, the pure NMI profiler can fail for
> a number of reasons, not just because the watchdog is in
> I/O APIC mode.
I assume you mean nmi_init? It doesn't check for the watchdog at all,
just if it knows the CPU and if it can profile
All the reasons it fails on (unknown CPU, no APIC) will imply that the lapic
based watchdog won't run either, because it relies on the same
perfctr hardware. The only case where it could fall into
this path is in IO-APIC nmi watchdog mode (and unknown CPU) and then again
the IO-APIC watchdog doesn't do the multiple frequencies thing, it always
runs with HZ.
Admittedly the logic is quite obscure.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
prev parent reply other threads:[~2009-02-23 6:16 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-29 23:58 x86's nmi_hz wrt. oprofile's nmi_timer_int.c David Miller
2009-01-30 15:01 ` Ingo Molnar
2009-01-30 21:54 ` David Miller
2009-02-02 23:14 ` David Miller
2009-02-03 12:27 ` Ingo Molnar
2009-02-22 17:06 ` Andi Kleen
2009-02-23 4:11 ` David Miller
2009-02-23 4:52 ` Andi Kleen
2009-02-23 5:59 ` David Miller
2009-02-23 6:34 ` Andi Kleen [this message]
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