linux-kernel - Re: [PATCH -mm -v2 00/12] mm, THP, swap: Delay splitting THP after swapped out

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Date:   Mon, 24 Jul 2017 08:57:48 +0800
From:   "Huang\, Ying" <ying.huang@...el.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     "Huang\, Ying" <ying.huang@...el.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        <linux-nvdimm@...ts.01.org>, Johannes Weiner <hannes@...xchg.org>,
        Minchan Kim <minchan@...nel.org>,
        Hugh Dickins <hughd@...gle.com>, Shaohua Li <shli@...nel.org>,
        Rik van Riel <riel@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Jens Axboe <axboe@...com>, Michal Hocko <mhocko@...nel.org>,
        Ming Lei <ming.lei@...hat.com>
Subject: Re: [PATCH -mm -v2 00/12] mm, THP, swap: Delay splitting THP after swapped out

Andrew Morton <akpm@...ux-foundation.org> writes:

> On Fri, 23 Jun 2017 15:12:51 +0800 "Huang, Ying" <ying.huang@...el.com> wrote:
>
>> From: Huang Ying <ying.huang@...el.com>
>> 
>> Hi, Andrew, could you help me to check whether the overall design is
>> reasonable?
>> 
>> Hi, Johannes and Minchan, Thanks a lot for your review to the first
>> step of the THP swap optimization!  Could you help me to review the
>> second step in this patchset?
>> 
>> Hi, Hugh, Shaohua, Minchan and Rik, could you help me to review the
>> swap part of the patchset?  Especially [01/12], [02/12], [03/12],
>> [04/12], [11/12], and [12/12].
>> 
>> Hi, Andrea and Kirill, could you help me to review the THP part of the
>> patchset?  Especially [01/12], [03/12], [07/12], [08/12], [09/12],
>> [11/12].
>> 
>> Hi, Johannes, Michal, could you help me to review the cgroup part of
>> the patchset?  Especially [08/12], [09/12], and [10/12].
>> 
>> And for all, Any comment is welcome!
>
> I guess it's time for a resend.  Folks, could we please get some more
> review&test going here?

Sure.  Will resend it ASAP.  And Thanks for reminding!

>> Because the THP swap writing support patch [06/12] needs to be rebased
>> on multipage bvec patchset which hasn't been merged yet.  The [06/12]
>> in this patchset is just a test patch and will be rewritten later.
>> The patchset depends on multipage bvec patchset too.
>
> Are these dependency issues any simpler now?

Ming Lei has sent the v2 of multipage bvec patchset on June 26th.  Jens
Axboe thinks the patchset will target v4.14.

https://lkml.org/lkml/2017/6/26/538

Best Regards,
Huang, Ying

>> This is the second step of THP (Transparent Huge Page) swap
>> optimization.  In the first step, the splitting huge page is delayed
>> from almost the first step of swapping out to after allocating the
>> swap space for the THP and adding the THP into the swap cache.  In the
>> second step, the splitting is delayed further to after the swapping
>> out finished.  The plan is to delay splitting THP step by step,
>> finally avoid splitting THP for the THP swapping out and swap out/in
>> the THP as a whole.
>> 
>> In the patchset, more operations for the anonymous THP reclaiming,
>> such as TLB flushing, writing the THP to the swap device, removing the
>> THP from the swap cache are batched.  So that the performance of
>> anonymous THP swapping out are improved.
>>