Re: [POLL] SLAB : Are the 32 and 192 bytes caches really usefull on x86_64 machines ?

[Alok kataria <alokkataria1@gmail.com>]

On 12/21/05, Eric Dumazet <dada1@cosmosbay.com> wrote:
> I wonder if the 32 and 192 bytes caches are worth to be declared in
> include/linux/kmalloc_sizes.h, at least on x86_64
>
> (x86_64 : PAGE_SIZE = 4096, L1_CACHE_BYTES = 64)
>
> On my machines, I can say that the 32 and 192 sizes could be avoided in favor
> in spending less cpu cycles in __find_general_cachep()
>
> Could some of you post the result of the following command on your machines :
>
> # grep "size-" /proc/slabinfo |grep -v DMA|cut -c1-40
>
> size-131072            0      0 131072
> size-65536             0      0  65536
> size-32768             2      2  32768
> size-16384             0      0  16384
> size-8192             13     13   8192
> size-4096            161    161   4096
> size-2048          40564  42976   2048
> size-1024            681    800   1024
> size-512           19792  37168    512
> size-256              81    105    256
> size-192            1218   1280    192
> size-64            31278  86907     64
> size-128            5457  10380    128
> size-32              594    784     32
>
> Thank you
>
> PS : I have no idea why the last lines (size-192, 64, 128, 32) are not ordered...

The size-32 and size-128 caches are created before any other cache, as
the array_caches (arraycache_init) and kmem_list3's structure come
from these cache.
Thus these caches are added to the cache_chain before other caches.
And s_show just walks this chain and prints info for the caches.

Before l3 was converted into a pointer (per node slabs) we could
intialize the caches in order as we knew that the arraycache_init will
always fit in the first cache.

Thanks & Regards,
Alok
>
> Eric
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