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From: Nick Piggin <>
To: Andi Kleen <>
Cc: Ingo Molnar <>,
	Linux Kernel Mailing List <>,
Subject: Re: [rfc][patch] x86-64 new smp_call_function design
Date: Wed, 27 Feb 2008 14:07:16 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Wed, Feb 27, 2008 at 02:04:18PM +0100, Andi Kleen wrote:
> > On a 2 socket, 8 core system, I see anywhere up to nearly 16x better
> > performance on a stress test. The common cases of call-all, and wait
> > are improved the least, however I think that if call-single and nowait
> > are turned into a high performance API, then new usages will pop up
> > (eg. I started this because I wanted to do "call single, nowait" calls
> > for migrating block IO completions back to submitting CPU; however I
> > am also interested in improving the "call all, wait" case for example
> > to improve vmalloc tlb flushing).
> TLB flushing at least on x86-64 should be already well optimized on its
> own. I would be surprised if you could do much better.

*vmalloc* TLB flushing. 

void flush_tlb_all(void)
        on_each_cpu(do_flush_tlb_all, NULL, 1, 1);

Of course we could use a new vector for it and speed it up a lot more,
but after my vmalloc improvements I think that would be a waste of a
vector at this point.

> > As far as I understand, calling a subset of online CPUs that is not all or
> > one, is used quite infrequently, so this might be OK.
> With cpusets and isolation etc. it is the normal case.

Oh really? Coming from what callers?

  reply	other threads:[~2008-02-27 13:07 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-27 12:42 Nick Piggin
2008-02-27 13:04 ` Andi Kleen
2008-02-27 13:07   ` Nick Piggin [this message]
2008-02-27 13:33     ` Andi Kleen
2008-03-16 14:33       ` Avi Kivity
2008-02-27 13:27 ` Ingo Molnar
2008-02-27 13:50   ` Nick Piggin
2008-02-27 15:02     ` Ingo Molnar
2008-02-27 22:14       ` Nick Piggin
2008-02-28  8:45         ` Ingo Molnar
2008-02-28 12:55           ` Andi Kleen

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