From: Will Deacon <will.deacon@arm.com>
To: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
John Stultz <john.stultz@linaro.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"patches@linaro.org" <patches@linaro.org>,
"linaro-kernel@lists.linaro.org" <linaro-kernel@lists.linaro.org>,
Sumit Semwal <sumit.semwal@linaro.org>,
Stephen Boyd <sboyd@codeaurora.org>,
Steven Rostedt <rostedt@goodmis.org>,
Russell King <linux@arm.linux.org.uk>,
Catalin Marinas <Catalin.Marinas@arm.com>
Subject: Re: [PATCH v4 2/5] sched_clock: Optimize cache line usage
Date: Mon, 9 Feb 2015 01:28:01 +0000 [thread overview]
Message-ID: <20150209012801.GA13969@arm.com> (raw)
In-Reply-To: <1423396960-4824-3-git-send-email-daniel.thompson@linaro.org>
On Sun, Feb 08, 2015 at 12:02:37PM +0000, Daniel Thompson wrote:
> Currently sched_clock(), a very hot code path, is not optimized to
> minimise its cache profile. In particular:
>
> 1. cd is not ____cacheline_aligned,
>
> 2. struct clock_data does not distinguish between hotpath and
> coldpath data, reducing locality of reference in the hotpath,
>
> 3. Some hotpath data is missing from struct clock_data and is marked
> __read_mostly (which more or less guarantees it will not share a
> cache line with cd).
>
> This patch corrects these problems by extracting all hotpath data
> into a separate structure and using ____cacheline_aligned to ensure
> the hotpath uses a single (64 byte) cache line.
Have you got any performance figures for this change, or is this just a
theoretical optimisation? It would be interesting to see what effect this
has on systems with 32-byte cachelines and also scenarios where there's
contention on the sequence counter.
Will
next prev parent reply other threads:[~2015-02-09 1:28 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-21 16:53 [RFC PATCH] sched_clock: Avoid tearing during read from NMI Daniel Thompson
2015-01-21 17:29 ` John Stultz
2015-01-21 20:20 ` Daniel Thompson
2015-01-21 20:58 ` Stephen Boyd
2015-01-22 13:06 ` [PATCH v2] sched_clock: Avoid deadlock " Daniel Thompson
2015-01-30 19:03 ` [PATCH v3 0/4] sched_clock: Optimize and avoid " Daniel Thompson
2015-01-30 19:03 ` [PATCH v3 1/4] sched_clock: Match scope of read and write seqcounts Daniel Thompson
2015-01-30 19:03 ` [PATCH v3 2/4] sched_clock: Optimize cache line usage Daniel Thompson
2015-02-05 1:14 ` Stephen Boyd
2015-02-05 10:21 ` Daniel Thompson
2015-01-30 19:03 ` [PATCH v3 3/4] sched_clock: Remove suspend from clock_read_data Daniel Thompson
2015-01-30 19:03 ` [PATCH v3 4/4] sched_clock: Avoid deadlock during read from NMI Daniel Thompson
2015-02-05 1:23 ` Stephen Boyd
2015-02-05 1:48 ` Steven Rostedt
2015-02-05 6:23 ` Stephen Boyd
2015-02-05 0:50 ` [PATCH v3 0/4] sched_clock: Optimize and avoid " Stephen Boyd
2015-02-05 9:05 ` Daniel Thompson
2015-02-08 12:09 ` Daniel Thompson
2015-02-09 22:08 ` Stephen Boyd
2015-02-08 12:02 ` [PATCH v4 0/5] " Daniel Thompson
2015-02-08 12:02 ` [PATCH v4 1/5] sched_clock: Match scope of read and write seqcounts Daniel Thompson
2015-02-08 12:02 ` [PATCH v4 2/5] sched_clock: Optimize cache line usage Daniel Thompson
2015-02-09 1:28 ` Will Deacon [this message]
2015-02-09 9:47 ` Daniel Thompson
2015-02-10 2:37 ` Stephen Boyd
2015-02-08 12:02 ` [PATCH v4 3/5] sched_clock: Remove suspend from clock_read_data Daniel Thompson
2015-02-08 12:02 ` [PATCH v4 4/5] sched_clock: Remove redundant notrace from update function Daniel Thompson
2015-02-08 12:02 ` [PATCH v4 5/5] sched_clock: Avoid deadlock during read from NMI Daniel Thompson
2015-02-13 3:49 ` [PATCH v4 0/5] sched_clock: Optimize and avoid " Stephen Boyd
2015-03-02 15:56 ` [PATCH v5 " Daniel Thompson
2015-03-02 15:56 ` [PATCH v5 1/5] sched_clock: Match scope of read and write seqcounts Daniel Thompson
2015-03-02 15:56 ` [PATCH v5 2/5] sched_clock: Optimize cache line usage Daniel Thompson
2015-03-02 15:56 ` [PATCH v5 3/5] sched_clock: Remove suspend from clock_read_data Daniel Thompson
2015-03-02 15:56 ` [PATCH v5 4/5] sched_clock: Remove redundant notrace from update function Daniel Thompson
2015-03-02 15:56 ` [PATCH v5 5/5] sched_clock: Avoid deadlock during read from NMI Daniel Thompson
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