From: "Huang\, Ying" <ying.huang@intel.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Huang, Ying" <ying.huang@intel.com>,
tim.c.chen@intel.com, dave.hansen@intel.com,
andi.kleen@intel.com, aaron.lu@intel.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Hugh Dickins <hughd@google.com>,
Shaohua Li <shli@kernel.org>, Minchan Kim <minchan@kernel.org>,
Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH -v2 01/10] swap: Change SWAPFILE_CLUSTER to 512
Date: Thu, 01 Sep 2016 16:04:57 -0700 [thread overview]
Message-ID: <87h99zdxwm.fsf@yhuang-mobile.sh.intel.com> (raw)
In-Reply-To: <20160901142246.631fe47a558bb7522f73c034@linux-foundation.org> (Andrew Morton's message of "Thu, 1 Sep 2016 14:22:46 -0700")
Andrew Morton <akpm@linux-foundation.org> writes:
> On Thu, 1 Sep 2016 08:16:54 -0700 "Huang, Ying" <ying.huang@intel.com> wrote:
>
>> From: Huang Ying <ying.huang@intel.com>
>>
>> In this patch, the size of the swap cluster is changed to that of the
>> THP (Transparent Huge Page) on x86_64 architecture (512). This is for
>> the THP swap support on x86_64. Where one swap cluster will be used to
>> hold the contents of each THP swapped out. And some information of the
>> swapped out THP (such as compound map count) will be recorded in the
>> swap_cluster_info data structure.
>>
>> In effect, this will enlarge swap cluster size by 2 times. Which may
>> make it harder to find a free cluster when the swap space becomes
>> fragmented. So that, this may reduce the continuous swap space
>> allocation and sequential write in theory. The performance test in 0day
>> show no regressions caused by this.
>>
>> --- a/mm/swapfile.c
>> +++ b/mm/swapfile.c
>> @@ -196,7 +196,7 @@ static void discard_swap_cluster(struct swap_info_struct *si,
>> }
>> }
>>
>> -#define SWAPFILE_CLUSTER 256
>> +#define SWAPFILE_CLUSTER 512
>> #define LATENCY_LIMIT 256
>>
>
> What happens to architectures which have different HPAGE_SIZE and/or
> PAGE_SIZE?
For the architecture with HPAGE_SIZE / PAGE_SIZE == 512 (for example
x86_64), the huge page swap optimizing will be turned on. For other
architectures, it will be turned off as before.
This mostly because I don't know whether it is a good idea to turn on
THP swap optimizing for the architectures other than x86_64. For
example, it appears that the huge page size is 8M (1<<23) on SPARC. But
I don't know whether 8M is too big for a swap cluster. And it appears
that the huge page size could be as large as 512M on MIPS.
Best Regards,
Huang, Ying
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next prev parent reply other threads:[~2016-09-01 23:05 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-01 15:16 [PATCH -v2 00/10] THP swap: Delay splitting THP during swapping out Huang, Ying
2016-09-01 15:16 ` [PATCH -v2 01/10] swap: Change SWAPFILE_CLUSTER to 512 Huang, Ying
2016-09-01 21:22 ` Andrew Morton
2016-09-01 23:04 ` Huang, Ying [this message]
2016-09-02 20:30 ` Andrew Morton
2016-09-02 20:37 ` Huang, Ying
2016-09-01 15:16 ` [PATCH -v2 02/10] mm, memcg: Add swap_cgroup_iter iterator Huang, Ying
2016-09-01 15:16 ` [PATCH -v2 03/10] mm, memcg: Support to charge/uncharge multiple swap entries Huang, Ying
2016-09-01 15:16 ` [PATCH -v2 04/10] mm, THP, swap: Add swap cluster allocate/free functions Huang, Ying
2016-09-01 15:16 ` [PATCH -v2 05/10] mm, THP, swap: Add get_huge_swap_page() Huang, Ying
2016-09-01 15:16 ` [PATCH -v2 06/10] mm, THP, swap: Support to clear SWAP_HAS_CACHE for huge page Huang, Ying
2016-09-01 15:17 ` [PATCH -v2 07/10] mm, THP, swap: Support to add/delete THP to/from swap cache Huang, Ying
2016-09-01 15:17 ` [PATCH -v2 08/10] mm, THP: Add can_split_huge_page() Huang, Ying
2016-09-01 15:17 ` [PATCH -v2 09/10] mm, THP, swap: Support to split THP in swap cache Huang, Ying
2016-09-01 15:17 ` [PATCH -v2 10/10] mm, THP, swap: Delay splitting THP during swap out Huang, Ying
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