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Re: [PATCH -mm -v7 1/9] mm, swap: Make swap cluster size same of THP size on x86_64

From "Huang\, Ying" <ying.huang@intel.com>
Newsgroups linux.kernel
Subject Re: [PATCH -mm -v7 1/9] mm, swap: Make swap cluster size same of THP size on x86_64
Date 2017-03-29 03:20 +0200
Message-ID <tqarf-7UU-3@gated-at.bofh.it> (permalink)
References <tpS1j-2ZP-5@gated-at.bofh.it> <tpS1j-2ZP-3@gated-at.bofh.it> <tq8St-6H1-9@gated-at.bofh.it>
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"Kirill A. Shutemov" <kirill@shutemov.name> writes:

> On Tue, Mar 28, 2017 at 01:32:01PM +0800, Huang, Ying 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.
>> 
>> For other architectures which want THP swap support,
>> ARCH_USES_THP_SWAP_CLUSTER need to be selected in the Kconfig file for
>> the architecture.
>
> Intreseting case could be architecture with HPAGE_PMD_NR < 256.
> Can current code pack more than one THP per claster.

No.  Only one THP for each swap cluster is supported.  But in current
implementation, if HPAGE_PMD_NR < 256, the swap cluster will be < 256
too.  The size of swap cluster will be exact same as HPAGE_PMD_NR.

Best Regards,
Huang, Ying

> If not we need to have BUILG_BUG_ON() to catch attempt of such enabling.

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Thread

[PATCH -mm -v7 1/9] mm, swap: Make swap cluster size same of THP size on x86_64 "Huang, Ying" <ying.huang@intel.com> - 2017-03-28 07:40 +0200
  Re: [PATCH -mm -v7 1/9] mm, swap: Make swap cluster size same of THP  size on x86_64 "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-03-29 01:40 +0200
    Re: [PATCH -mm -v7 1/9] mm, swap: Make swap cluster size same of THP size on x86_64 "Huang\, Ying" <ying.huang@intel.com> - 2017-03-29 03:20 +0200
  Re: [PATCH -mm -v7 1/9] mm, swap: Make swap cluster size same of THP  size on x86_64 Johannes Weiner <hannes@cmpxchg.org> - 2017-03-29 19:00 +0200
    Re: [PATCH -mm -v7 1/9] mm, swap: Make swap cluster size same of THP size on x86_64 "Huang\, Ying" <ying.huang@intel.com> - 2017-03-30 02:50 +0200
      Re: [PATCH -mm -v7 1/9] mm, swap: Make swap cluster size same of THP  size on x86_64 Johannes Weiner <hannes@cmpxchg.org> - 2017-03-31 17:00 +0200
        Re: [PATCH -mm -v7 1/9] mm, swap: Make swap cluster size same of THP size on x86_64 "Huang\, Ying" <ying.huang@intel.com> - 2017-04-01 05:30 +0200

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