Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations

From	Minchan Kim <minchan@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations
Date	2017-01-03 05:40 +0100
Message-ID	<sVp3c-G9-9@gated-at.bofh.it> (permalink)
References	<sMAAx-8eJ-15@gated-at.bofh.it> <sSUGd-7AR-13@gated-at.bofh.it> <sVd22-r2-7@gated-at.bofh.it>
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Hi Jan,

On Mon, Jan 02, 2017 at 04:48:41PM +0100, Jan Kara wrote:
> Hi,
> 
> On Tue 27-12-16 16:45:03, Minchan Kim wrote:
> > > Patch 3 splits the swap cache radix tree into 64MB chunks, reducing
> > >         the rate that we have to contende for the radix tree.
> > 
> > To me, it's rather hacky. I think it might be common problem for page cache
> > so can we think another generalized way like range_lock? Ccing Jan.
> 
> I agree on the hackyness of the patch and that page cache would suffer with
> the same contention (although the files are usually smaller than swap so it
> would not be that visible I guess). But I don't see how range lock would
> help here - we need to serialize modifications of the tree structure itself
> and that is difficult to achieve with the range lock. So what you would
> need is either a different data structure for tracking swap cache entries
> or a finer grained locking of the radix tree.

Thanks for the comment, Jan.

I think there are more general options. One is to shrink batching pages like
Mel and Tim had approached.

https://patchwork.kernel.org/patch/9008421/
https://patchwork.kernel.org/patch/9322793/

Or concurrent page cache by peter.

https://www.kernel.org/doc/ols/2007/ols2007v2-pages-311-318.pdf

Ccing Nick who might have an interest on lockless page cache.

Thanks.

Thread

Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations Minchan Kim <minchan@kernel.org> - 2016-12-27 08:50 +0100
  Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations "Huang\, Ying" <ying.huang@intel.com> - 2016-12-28 03:00 +0100
    Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations Minchan Kim <minchan@kernel.org> - 2016-12-28 03:40 +0100
      Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations "Huang\, Ying" <ying.huang@intel.com> - 2016-12-28 04:20 +0100
        Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations "Huang\, Ying" <ying.huang@intel.com> - 2016-12-28 04:40 +0100
          Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations Minchan Kim <minchan@kernel.org> - 2016-12-28 05:10 +0100
            Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations "Huang\, Ying" <ying.huang@intel.com> - 2016-12-28 06:00 +0100
  Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations Jan Kara <jack@suse.cz> - 2017-01-02 16:50 +0100
    Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations Minchan Kim <minchan@kernel.org> - 2017-01-03 05:40 +0100
      Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations "Huang\, Ying" <ying.huang@intel.com> - 2017-01-03 06:50 +0100
        Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations Minchan Kim <minchan@kernel.org> - 2017-01-05 07:30 +0100
      Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations Tim Chen <tim.c.chen@linux.intel.com> - 2017-01-03 18:50 +0100
  Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations "Huang\, Ying" <ying.huang@intel.com> - 2017-01-05 02:40 +0100
    Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations "Huang\, Ying" <ying.huang@intel.com> - 2017-01-05 08:00 +0100
    Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations Minchan Kim <minchan@kernel.org> - 2017-01-05 08:00 +0100

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