linux-kernel - Re: [PATCH 4/6] x86: mm: trace tlb flushes

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Message-ID: <5356DCEF.3050506@redhat.com>
Date:	Tue, 22 Apr 2014 17:19:43 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Dave Hansen <dave@...1.net>, x86@...nel.org
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
	mgorman@...e.de, ak@...ux.intel.com, alex.shi@...aro.org,
	dave.hansen@...ux.intel.com
Subject: Re: [PATCH 4/6] x86: mm: trace tlb flushes

On 04/21/2014 02:24 PM, Dave Hansen wrote:
> From: Dave Hansen <dave.hansen@...ux.intel.com>
> 
> We don't have any good way to figure out what kinds of flushes
> are being attempted.  Right now, we can try to use the vm
> counters, but those only tell us what we actually did with the
> hardware (one-by-one vs full) and don't tell us what was actually
> _requested_.
> 
> This allows us to select out "interesting" TLB flushes that we
> might want to optimize (like the ranged ones) and ignore the ones
> that we have very little control over (the ones at context
> switch).
> 
> Also, since we have a pair of tracepoint calls in
> flush_tlb_mm_range(), we can time the deltas between them to make
> sure that we got the "invlpg vs. global flush" balance correct in
> practice.
> 
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>

Acked-by: Rik van Riel <riel@...hat.com>


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