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From: Johannes Weiner <hannes@cmpxchg.org>
To: "Huang, Ying" <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -mm -v9 2/3] mm, THP, swap: Check whether THP can be split firstly
Date: Thu, 20 Apr 2017 16:50:35 -0400	[thread overview]
Message-ID: <20170420205035.GA13229@cmpxchg.org> (raw)
In-Reply-To: <87efwnrjfg.fsf@yhuang-dev.intel.com>

On Thu, Apr 20, 2017 at 08:50:43AM +0800, Huang, Ying wrote:
> Johannes Weiner <hannes@cmpxchg.org> writes:
> > On Wed, Apr 19, 2017 at 03:06:24PM +0800, Huang, Ying wrote:
> >> With the patchset, the swap out throughput improves 3.6% (from about
> >> 4.16GB/s to about 4.31GB/s) in the vm-scalability swap-w-seq test case
> >> with 8 processes.  The test is done on a Xeon E5 v3 system.  The swap
> >> device used is a RAM simulated PMEM (persistent memory) device.  To
> >> test the sequential swapping out, the test case creates 8 processes,
> >> which sequentially allocate and write to the anonymous pages until the
> >> RAM and part of the swap device is used up.
> >> 
> >> Cc: Johannes Weiner <hannes@cmpxchg.org>
> >> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> >> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> [for can_split_huge_page()]
> >
> > How often does this actually happen in practice? Because all that this
> > protects us from is trying to allocate a swap cluster - which with the
> > si->free_clusters list really isn't all that expensive - and return it
> > again. Unless this happens all the time in practice, this optimization
> > seems misplaced.
>
> To my surprise too, I found this patch has measurable impact in my
> test.  The swap out throughput improves 3.6% in the vm-scalability
> swap-w-seq test case with 8 processes.  Details are in the original
> patch description.

Yeah I think that justifies it.

The changelog says "the patchset", I didn't realize this is the gain
from just this patch alone. Care to update that?

Thanks!

  reply	other threads:[~2017-04-20 20:50 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-19  7:06 [PATCH -mm -v9 0/3] THP swap: Delay splitting THP during swapping out Huang, Ying
2017-04-19  7:06 ` [PATCH -mm -v9 1/3] mm, THP, swap: Delay splitting THP during swap out Huang, Ying
2017-04-19 15:52   ` Johannes Weiner
2017-04-20  0:43     ` Huang, Ying
2017-04-21  6:11   ` Balbir Singh
2017-04-21  7:21     ` Huang, Ying
2017-04-21 14:08     ` Johannes Weiner
2017-04-22  0:07       ` Huang, Ying
2017-04-19  7:06 ` [PATCH -mm -v9 2/3] mm, THP, swap: Check whether THP can be split firstly Huang, Ying
2017-04-19 16:13   ` Johannes Weiner
2017-04-20  0:50     ` Huang, Ying
2017-04-20 20:50       ` Johannes Weiner [this message]
2017-04-21  0:34         ` Huang, Ying
2017-04-19  7:06 ` [PATCH -mm -v9 3/3] mm, THP, swap: Enable THP swap optimization only if has compound map Huang, Ying
2017-04-19 16:00   ` Johannes Weiner
2017-04-20  0:51     ` Huang, Ying

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