From: Peter Zijlstra <peterz@infradead.org>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@elte.hu>,
Thomas Gleixner <tglx@linutronix.de>,
James Bottomley <James.Bottomley@HansenPartnership.com>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
ltt-dev@lists.casi.polymtl.ca
Subject: Re: LTTng finds abnormally long APIC interrupt handler : 58.2 ms
Date: Sat, 09 Aug 2008 09:14:25 +0200 [thread overview]
Message-ID: <1218266065.29098.36.camel@lappy.programming.kicks-ass.net> (raw)
In-Reply-To: <20080808231126.GA23766@Krystal>
On Fri, 2008-08-08 at 19:11 -0400, Mathieu Desnoyers wrote:
> The basic question that arises from this trace is : is it normal for
> find_usage_backwards to be called ~8500 times during a spinlock ?
Yes and no - its O(n^2) graph walking. That said, David Miller did a
cool patch that reduces the graph walk by not doing the same subgraph
over and over again. Look at this series:
http://lkml.org/lkml/2008/8/4/175
Andrew picked all that up - so it should be in the next -mm.
It also contains a new scheduler run-queue annotation which should
greatly reduce the chain length, adding to even more benefit.
prev parent reply other threads:[~2008-08-09 7:15 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-05 18:20 LTTng finds abnormally long APIC interrupt handler : 58.2 ms Mathieu Desnoyers
2008-08-05 19:24 ` Steven Rostedt
2008-08-07 16:09 ` Mathieu Desnoyers
2008-08-07 17:41 ` Steven Rostedt
2008-08-07 18:15 ` Frank Ch. Eigler
2008-08-07 18:24 ` Mathieu Desnoyers
2008-08-07 18:32 ` Steven Rostedt
2008-08-08 23:11 ` Mathieu Desnoyers
2008-08-09 7:14 ` Peter Zijlstra [this message]
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