From: Andi Kleen <andi@firstfloor.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>,
Ingo Molnar <mingo@kernel.org>, Mel Gorman <mgorman@suse.de>,
Andrew Morton <akpm@linux-foundation.org>,
Rik van Riel <riel@redhat.com>, Hugh Dickins <hughd@google.com>,
Minchan Kim <minchan@kernel.org>,
Andi Kleen <andi@firstfloor.org>, H Peter Anvin <hpa@zytor.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 0/3] TLB flush multiple pages per IPI v5
Date: Wed, 10 Jun 2015 15:13:54 +0200 [thread overview]
Message-ID: <20150610131354.GO19417@two.firstfloor.org> (raw)
In-Reply-To: <CA+55aFz6b5pG9tRNazk8ynTCXS3whzWJ_737dt1xxAHDf1jASQ@mail.gmail.com>
On Tue, Jun 09, 2015 at 02:54:01PM -0700, Linus Torvalds wrote:
> On Tue, Jun 9, 2015 at 2:14 PM, Dave Hansen <dave.hansen@intel.com> wrote:
> >
> > The 0 cycle TLB miss was also interesting. It goes back up to something
> > reasonable if I put the mb()/mfence's back.
>
> So I've said it before, and I'll say it again: Intel does really well
> on TLB fills.
Assuming the page tables are cache-hot... And hot here does not mean
L3 cache, but higher. But a memory intensive workload can easily
violate that.
That's why I'm dubious of all these micro benchmarks. They won't be
clearing caches. They generate unrealistic conditions in the CPU
pipeline and overestimate the cost of the flushes.
The only good way to measure TLB costs is macro benchmarks.
-Andi
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next prev parent reply other threads:[~2015-06-10 13:13 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-08 12:50 Mel Gorman
2015-06-08 12:50 ` [PATCH 1/3] x86, mm: Trace when an IPI is about to be sent Mel Gorman
2015-06-08 12:50 ` [PATCH 2/3] mm: Send one IPI per CPU to TLB flush multiple pages that were recently unmapped Mel Gorman
2015-06-08 22:38 ` Andrew Morton
2015-06-09 11:07 ` Mel Gorman
2015-06-08 12:50 ` [PATCH 3/3] mm: Defer flush of writable TLB entries Mel Gorman
2015-06-08 17:45 ` [PATCH 0/3] TLB flush multiple pages per IPI v5 Ingo Molnar
2015-06-08 18:21 ` Dave Hansen
2015-06-08 19:52 ` Ingo Molnar
2015-06-08 20:03 ` Ingo Molnar
2015-06-08 21:07 ` Dave Hansen
2015-06-08 21:50 ` Ingo Molnar
2015-06-09 8:47 ` Mel Gorman
2015-06-09 10:32 ` Ingo Molnar
2015-06-09 11:20 ` Mel Gorman
2015-06-09 12:43 ` Ingo Molnar
2015-06-09 13:05 ` Mel Gorman
2015-06-10 8:51 ` Ingo Molnar
2015-06-10 9:08 ` Ingo Molnar
2015-06-10 10:15 ` Mel Gorman
2015-06-11 15:26 ` Ingo Molnar
2015-06-10 9:19 ` Mel Gorman
2015-06-09 15:34 ` Dave Hansen
2015-06-09 16:49 ` Dave Hansen
2015-06-09 21:14 ` Dave Hansen
2015-06-09 21:54 ` Linus Torvalds
2015-06-09 22:32 ` Mel Gorman
2015-06-09 22:35 ` Mel Gorman
2015-06-10 13:13 ` Andi Kleen [this message]
2015-06-10 16:17 ` Linus Torvalds
2015-06-10 16:42 ` Linus Torvalds
2015-06-10 17:24 ` Mel Gorman
2015-06-10 17:31 ` Linus Torvalds
2015-06-10 18:08 ` Josh Boyer
2015-06-10 17:07 ` Mel Gorman
2015-06-21 20:22 ` Kirill A. Shutemov
2015-06-25 11:48 ` Ingo Molnar
2015-06-25 18:36 ` Linus Torvalds
2015-06-25 19:15 ` Vlastimil Babka
2015-06-25 22:04 ` Linus Torvalds
2015-06-25 18:46 ` Dave Hansen
2015-06-26 9:08 ` Ingo Molnar
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