linux-kernel - [PATCH 0 of 9] x86/smp function calls: convert x86 tlb flushes to use function calls [POST 2]

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Date:	Mon, 18 Aug 2008 11:23:37 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
	Andi Kleen <andi@...stfloor.org>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: [PATCH 0 of 9] x86/smp function calls: convert x86 tlb flushes to use
	function calls [POST 2]

This series:
 - adds a simple debugfs profiling entry for cross-cpu tlb flushes
 - converts them to using smp_call_function_mask
 - unifies 32 and 64-bit tlb flushes
 - converts smp_call_function to using multiple queues (using the now
   freed vectors)
 - allows config-time adjustment of the number of queues
 - adds a kernel parameter to disable multi-queue in case it causes
   problems

The main concern is whether using smp_call_function adds an
unacceptible performance hit to cross-cpu tlb flushes.  My limited
measurements show a ~35% regression in latency for a particular flush;
it would be interesting to try this on a wider range of hardware.  I
gather the effect tlb flush performance is very application specific
as well, but I'm not sure what benchmarks show what effects.

Trading off agains the latency of a given flush, the smp_function_call
mechanism allows multiple requests to be queued, and so may improve
throughput on a system-wide basis.

So, I'd like people to try this out and see what performance effects it
has.

Thanks,
	J

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