linux-kernel - x86: Is there still value in having a special tlb flush IPI vector?

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Message-ID: <488E534F.2030204@goop.org>
Date:	Mon, 28 Jul 2008 16:16:31 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Jens Axboe <jens.axboe@...cle.com>, Andi Kleen <ak@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: x86: Is there still value in having a special tlb flush IPI vector?

Now that normal smp_function_call is no longer an enormous bottleneck, 
is there still value in having a specialised IPI vector for tlb 
flushes?  It seems like quite a lot of duplicate code.

The 64-bit tlb flush multiplexes the various cpus across 8 vectors to 
increase scalability. If this is a big issue, then the smp function call 
code can (and should) do the same thing.  (Though looking at it more 
closely, the way the code uses the 8 vectors is actually a less general 
way of doing what smp_call_function is doing anyway.)

Thoughts?

(And uv should definitely be hooking pvops if it wants its own 
flush_tlb_others; vsmp sets the precedent for a subarch-like use of pvops.)

    J
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