From: Ingo Molnar <mingo@kernel.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: linux-kernel@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Arnaldo Carvalho de Melo <acme@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 4/5] perf, x86: Support full width counting v3
Date: Fri, 22 Feb 2013 14:46:30 +0100 [thread overview]
Message-ID: <20130222134630.GA8960@gmail.com> (raw)
In-Reply-To: <1361213287-7636-5-git-send-email-andi@firstfloor.org>
* Andi Kleen <andi@firstfloor.org> wrote:
> From: Andi Kleen <ak@linux.intel.com>
>
> Recent Intel CPUs like Haswell and IvyBridge have a new
> alternative MSR range for perfctrs that allows writing the
> full counter width. Enable this range if the hardware reports
> it using a new capability bit.
>
> This lowers the overhead of perf stat slightly because it has
> to do less interrupts to accumulate the counter value. On
> Haswell it also avoids some problems with TSX aborting when
> the end of the counter range is reached.
The changelog does not adequately explain why this patch is
critical for basic Haswell enablement. "Avoids some problems
with TSX aborting" is not very helpful.
Thanks,
Ingo
next prev parent reply other threads:[~2013-02-22 13:46 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-18 18:48 Basic perf PMU support for Haswell v8 Andi Kleen
2013-02-18 18:48 ` [PATCH 1/5] perf, x86: Add Haswell PEBS record support v4 Andi Kleen
2013-02-18 18:48 ` [PATCH 2/5] perf, x86: Basic Haswell PMU support v5 Andi Kleen
2013-02-18 18:48 ` [PATCH 3/5] perf, x86: Basic Haswell PEBS support v4 Andi Kleen
2013-02-18 18:48 ` [PATCH 4/5] perf, x86: Support full width counting v3 Andi Kleen
2013-02-22 13:46 ` Ingo Molnar [this message]
2013-02-22 15:19 ` Andi Kleen
2013-02-24 12:07 ` Ingo Molnar
2013-02-18 18:48 ` [PATCH 5/5] perf, x86: Move NMI clearing to end of PMI handler after the counter registers are reset Andi Kleen
-- strict thread matches above, loose matches on Subject: below --
2013-02-13 16:08 Basic perf PMU support for Haswell v7 Andi Kleen
2013-02-13 16:08 ` [PATCH 4/5] perf, x86: Support full width counting v3 Andi Kleen
2013-02-12 22:04 Basic perf PMU support for Haswell v6 Andi Kleen
2013-02-12 22:04 ` [PATCH 4/5] perf, x86: Support full width counting v3 Andi Kleen
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