Christoph Lameter a =E9crit :
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> On Thu, 23 Oct 2008, Eric Dumazet wrote:
>=20
>>> SLUB touches objects by default when allocating. And it does it=20
>>> immediately in slab_alloc() in order to retrieve the pointer to the=20
>>> next object. So there is no point of hinting there right now.
>>>
>>
>> Please note SLUB touches by reading object.
>>
>> prefetchw() gives a hint to cpu saying this cache line is going to be =

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>> *modified*, even
>> if first access is a read. Some architectures can save some bus=20
>> transactions, acquiring
>> the cache line in an exclusive way instead of shared one.
>=20
> Most architectures actually can do that. Its probably worth to run some=
=20
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> tests with that. Conversion of a cacheline from shared to exclusive can=
=20
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> cost something.
>=20

Please check following patch as a followup

[PATCH] slub: slab_alloc() can use prefetchw()

Most kmalloced() areas are initialized/written right after allocation.

prefetchw() gives a hint to cpu saying this cache line is going to be
*modified*, even if first access is a read.

Some architectures can save some bus transactions, acquiring
the cache line in an exclusive way instead of shared one.

Same optimization was done in 2005 on SLAB in commit=20
34342e863c3143640c031760140d640a06c6a5f8=20
([PATCH] mm/slab.c: prefetchw the start of new allocated objects)

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>