From: Andrew Morton <akpm@osdl.org>
To: Ravikiran G Thirumalai <kiran@in.ibm.com>
Cc: steiner@sgi.com, linux-kernel@vger.kernel.org
Subject: Re: hot cache line due to note_interrupt()
Date: Tue, 11 Nov 2003 11:58:04 -0800 [thread overview]
Message-ID: <20031111115804.4aaafd28.akpm@osdl.org> (raw)
In-Reply-To: <20031111082915.GC1130@llm08.in.ibm.com>
Ravikiran G Thirumalai <kiran@in.ibm.com> wrote:
>
> On Mon, Nov 10, 2003 at 03:58:44PM -0600, Jack Steiner wrote:
> >
> > I dont know the background on note_interrupt() in arch/ia64/kernel/irq.c,
> > but I had to disable the function on our large systems (IA64).
> >
> > The function updates a counter in the irq_desc_t table. An entry in this table
> > is shared by all cpus that take a specific interrupt #. For most interrupt #'s,
> > this is a problem but it is prohibitive for the timer tick on big systems.
> >
> > Updating the counter causes a cache line to be bounced between
> > cpus at a rate of at least HZ*active_cpus. (The number of bus transactions
>
> The answer to this is probably alloc_percpu for the counters.
Or just make noirqdebug the default.
The note_interrupt() stuff is only useful for diagnosing mysterious lockups
(and hasn't proven useful for that, actually). It should be disabled for
production use.
next prev parent reply other threads:[~2003-11-11 19:54 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-10 21:58 hot cache line due to note_interrupt() Jack Steiner
2003-11-10 23:00 ` Anton Blanchard
2003-11-11 8:29 ` Ravikiran G Thirumalai
2003-11-11 16:25 ` Anton Blanchard
2003-11-11 19:58 ` Andrew Morton [this message]
2003-11-14 17:45 ` Jack Steiner
2003-11-14 17:57 ` Andrew Morton
2003-11-14 18:11 ` Jack Steiner
2003-11-14 18:10 ` David Mosberger
2003-11-14 18:17 ` Linus Torvalds
2003-11-15 5:18 ` Jeff Garzik
2003-11-14 19:10 ` Anton Blanchard
2003-11-14 19:28 ` Mike Fedyk
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