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

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Message-Id: <20170721162129.077f7d9b4c77c8593e47aed9@linux-foundation.org>
Date:   Fri, 21 Jul 2017 16:21:29 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     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

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?

> 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?

> 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.
>