Re: [PATCH] z3fold: the 3-fold allocator for compressed pages

From	Vitaly Wool <vitalywool@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] z3fold: the 3-fold allocator for compressed pages
Date	2016-04-14 20:30 +0200
Message-ID	<rnUbE-6hd-17@gated-at.bofh.it> (permalink)
References	(1 earlier) <rnL8m-7nM-5@gated-at.bofh.it> <rnRQu-4b1-9@gated-at.bofh.it> <rnRQu-4b1-7@gated-at.bofh.it> <rnTyY-5JF-55@gated-at.bofh.it> <rnTSi-69H-15@gated-at.bofh.it>
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>> On Thu, Apr 14, 2016 at 5:53 PM, Seth Jennings <sjenning@redhat.com> wrote:

<snip>
>>> This also means that the unbuddied list is broken in this
>>> implementation.  num_free_chunks() is calculating the _total_ free
>>> space in the page.  But that is not that the _usable_ free space by a
>>> single object, if the middle object has partitioned that free space.
>>
>> Once again, there is the code in z3fold_free() that makes sure the
>> free space within the page is contiguous so I don't think the
>> unbuddied list is, or will be, broken.
>
> Didn't see the relocation before.  However, that brings up another
> question.  How is the code moving objects when the location of that
> object is encoded in the handle that has already been given to the
> user?

Relocation is only necessary when there is one remaining object and it
is in the middle. In that case the 'first_num' variable is incremented
so its handle already given to user will be resolved as the first
object and not the middle.

~vitaly

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[PATCH] z3fold: the 3-fold allocator for compressed pages Vitaly Wool <vitalywool@gmail.com> - 2016-04-14 10:10 +0200
  Re: [PATCH] z3fold: the 3-fold allocator for compressed pages Vlastimil Babka <vbabka@suse.cz> - 2016-04-14 10:50 +0200
    Re: [PATCH] z3fold: the 3-fold allocator for compressed pages Seth Jennings <sjenning@redhat.com> - 2016-04-14 18:00 +0200
      Re: [PATCH] z3fold: the 3-fold allocator for compressed pages Vitaly Wool <vitalywool@gmail.com> - 2016-04-14 19:50 +0200
        Re: [PATCH] z3fold: the 3-fold allocator for compressed pages Seth Jennings <sjenning@redhat.com> - 2016-04-14 20:10 +0200
          Re: [PATCH] z3fold: the 3-fold allocator for compressed pages Vitaly Wool <vitalywool@gmail.com> - 2016-04-14 20:30 +0200

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