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Re: [PATCH 09/16] mm/slab: put the freelist at the end of slab page

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2016-01-15 0:26 GMT+09:00 Christoph Lameter <cl@linux.com>:
> On Thu, 14 Jan 2016, Joonsoo Kim wrote:
>
>> Currently, the freelist is at the front of slab page. This requires
>> extra space to meet object alignment requirement. If we put the freelist
>> at the end of slab page, object could start at page boundary and will
>> be at correct alignment. This is possible because freelist has
>> no alignment constraint itself.
>>
>> This gives us two benefits. It removes extra memory space
>> for the freelist alignment and remove complex calculation
>> at cache initialization step. I can't think notable drawback here.
>
>
> The third one is that the padding space at the end of the slab could
> actually be used for the freelist if it fits.

Yes.

> The drawback may be that the location of the freelist at the beginning of
> the page is more cache effective because the cache prefetcher may be able
> to get the following cachelines and effectively hit the first object.
> However, this is rather dubious speculation.

I think so, too. :)
If then, could you give me an ack?

Thanks.

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[PATCH 00/16] mm/slab: introduce new freed objects management way, OBJFREELIST_SLAB Joonsoo Kim <js1304@gmail.com> - 2016-01-14 06:30 +0100
  [PATCH 01/16] mm/slab: fix stale code comment Joonsoo Kim <js1304@gmail.com> - 2016-01-14 06:30 +0100
    Re: [PATCH 01/16] mm/slab: fix stale code comment Christoph Lameter <cl@linux.com> - 2016-01-14 16:30 +0100
  [PATCH 06/16] mm/slab: clean-up DEBUG_PAGEALLOC processing code Joonsoo Kim <js1304@gmail.com> - 2016-01-14 06:30 +0100
  [PATCH 08/16] mm/slab: remove object status buffer for DEBUG_SLAB_LEAK Joonsoo Kim <js1304@gmail.com> - 2016-01-14 06:30 +0100
  [PATCH 09/16] mm/slab: put the freelist at the end of slab page Joonsoo Kim <js1304@gmail.com> - 2016-01-14 06:30 +0100
    Re: [PATCH 09/16] mm/slab: put the freelist at the end of slab  page Christoph Lameter <cl@linux.com> - 2016-01-14 16:40 +0100
      Re: [PATCH 09/16] mm/slab: put the freelist at the end of slab page Joonsoo Kim <js1304@gmail.com> - 2016-01-14 17:30 +0100
    Re: [PATCH 09/16] mm/slab: put the freelist at the end of slab  page Christoph Lameter <cl@linux.com> - 2016-01-14 18:20 +0100
  [PATCH 12/16] mm/slab: do not change cache size if debug pagealloc isn't possible Joonsoo Kim <js1304@gmail.com> - 2016-01-14 06:30 +0100
  [PATCH 14/16] mm/slab: factor out slab list fixup code Joonsoo Kim <js1304@gmail.com> - 2016-01-14 06:30 +0100

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