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From: "Huang\, Ying" <ying.huang@intel.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Huang\, Ying" <ying.huang@intel.com>,
	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: Fri, 21 Apr 2017 08:34:22 +0800	[thread overview]
Message-ID: <87r30mha41.fsf@yhuang-dev.intel.com> (raw)
In-Reply-To: <20170420205035.GA13229@cmpxchg.org> (Johannes Weiner's message of "Thu, 20 Apr 2017 16:50:35 -0400")

Johannes Weiner <hannes@cmpxchg.org> writes:

> 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?

Sorry for confusing, will update it in the next version.

Best Regards,
Huang, Ying

> Thanks!

  reply	other threads:[~2017-04-21  0:34 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
2017-04-21  0:34         ` Huang, Ying [this message]
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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