From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Waiman Long <Waiman.Long@hp.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Scott J Norton <scott.norton@hp.com>
Subject: Re: [PATCH v2 2/2] mm, thp: replace smp_mb after atomic_add by smp_mb__after_atomic
Date: Wed, 18 Jun 2014 15:17:31 +0300 [thread overview]
Message-ID: <20140618121731.GA5957@node.dhcp.inet.fi> (raw)
In-Reply-To: <1403044679-9993-3-git-send-email-Waiman.Long@hp.com>
On Tue, Jun 17, 2014 at 06:37:59PM -0400, Waiman Long wrote:
> In some architectures like x86, atomic_add() is a full memory
> barrier. In that case, an additional smp_mb() is just a waste of time.
> This patch replaces that smp_mb() by smp_mb__after_atomic() which
> will avoid the redundant memory barrier in some architectures.
>
> With a 3.16-rc1 based kernel, this patch reduced the execution time
> of breaking 1000 transparent huge pages from 38,245us to 30,964us. A
> reduction of 19% which is quite sizeable. It also reduces the %cpu
> time of the __split_huge_page_refcount function in the perf profile
> from 2.18% to 1.15%.
>
> Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
--
Kirill A. Shutemov
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prev parent reply other threads:[~2014-06-18 12:20 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-17 22:37 [PATCH v2 0/2] mm, thp: two THP splitting performance fixes Waiman Long
2014-06-17 22:37 ` [PATCH v2 1/2] mm, thp: move invariant bug check out of loop in __split_huge_page_map Waiman Long
2014-06-18 12:24 ` Kirill A. Shutemov
2014-06-18 15:31 ` Waiman Long
2014-06-17 22:37 ` [PATCH v2 2/2] mm, thp: replace smp_mb after atomic_add by smp_mb__after_atomic Waiman Long
2014-06-18 12:17 ` Kirill A. Shutemov [this message]
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