Messages in this thread | | | Date | Sat, 19 Oct 2013 00:12:54 +0900 | Subject | Re: [PATCH v2 3/5] slab: restrict the number of objects in a slab | From | JoonSoo Kim <> |
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2013/10/18 Christoph Lameter <cl@linux.com>: > n Thu, 17 Oct 2013, Joonsoo Kim wrote: > >> To prepare to implement byte sized index for managing the freelist >> of a slab, we should restrict the number of objects in a slab to be less >> or equal to 256, since byte only represent 256 different values. >> Setting the size of object to value equal or more than newly introduced >> SLAB_MIN_SIZE ensures that the number of objects in a slab is less or >> equal to 256 for a slab with 1 page. > > Ok so that results in a mininum size object size of 2^(12 - 8) = 2^4 == > 16 bytes on x86. This is not true for order 1 pages (which SLAB also > supports) where we need 32 bytes.
According to current slab size calculating logic, slab whose object size is less or equal to 16 bytes use only order 0 page. So there is no problem.
> Problems may arise on PPC or IA64 where the page size may be larger than > 64K. With 64K we have a mininum size of 2^(16 - 8) = 256 bytes. For those > arches we may need 16 bit sized indexes. Maybe make that compile time > determined base on page size? > 64KByte results in 16 bit sized indexes?
Okay. I will try it.
> Otherwise I like this approach. Simplifies a lot and its very cache > friendly.
Thanks.
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