linux-kernel - Re: [PATCH v5 6/7] x86/tlb: optimizing flush_tlb

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Message-ID: <CAJRGBZy0S_fg3GY4S5CG-2SWv5AG1jMrcMMqCiTg=7xyD1mrzQ@mail.gmail.com>
Date:	Tue, 15 May 2012 20:58:54 +0800
From:	Luming Yu <luming.yu@...il.com>
To:	Nick Piggin <npiggin@...il.com>
Cc:	Alex Shi <alex.shi@...el.com>, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, arnd@...db.de,
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	jcm@...masters.org
Subject: Re: [PATCH v5 6/7] x86/tlb: optimizing flush_tlb_mm

On Tue, May 15, 2012 at 5:17 PM, Nick Piggin <npiggin@...il.com> wrote:
> On 15 May 2012 19:15, Nick Piggin <npiggin@...il.com> wrote:
>> So this should go to linux-arch...
>>
>> On 15 May 2012 18:55, Alex Shi <alex.shi@...el.com> wrote:
>>> Not every flush_tlb_mm execution moment is really need to evacuate all
>>> TLB entries, like in munmap, just few 'invlpg' is better for whole
>>> process performance, since it leaves most of TLB entries for later
>>> accessing.
>
> Did you have microbenchmarks for this like your mprotect numbers,
> by the way? Test munmap numbers and see how that looks. Also,

Might be off topic, but I just spent few minutes to test out the difference
between write CR3 vs. invlpg on a pretty old but still reliable P4 desktop
with my simple hardware latency and bandwidth test tool I posted for
RFC several weeks ago on LKML.

Both __native_flush_tlb() and __native_flush_tlb_single(...)
introduced roughly 1 ns  latency to tsc sampling executed in
stop_machine_context in two logical CPUs

Just to fuel the discussion. :-)

Cheers,
/l
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