Re: PATCH: kmalloc packet slab

[Manfred Spraul]

> Why 1620 bytes ?
Because then 5 objects will fit into one 8 kB memory block:
5*1620+slab control structure.

> Most drivers allocate packet_size + 2 bytes.
> dev_alloc_skb adds another 16 bytes, finally alloc_skb adds
> sizeof(struct skb_shared_info). 
>
>  
>
> (32bit): 1514b + 2b + 16b + 160b = 1692b
> (64bit): 1514b + 2b + 16b + 312b = 1844b
>
>  
Hmm. If the shared_info is that large then the patch won't help much.

Alan - what is printed in the /proc/slabinfo line for the new cache?
- 1620 bytes is probably a bit too much for archs with 128 byte cache 
lines and 8 kB pages. If I've calculated correctly, only 4 will fit into 
one page.
- if the shared info is really that large - is the patch actually useful?

--
   Manfred

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