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Message-ID: <41D04977.2040902@colorfullife.com>
Date: Mon, 27 Dec 2004 18:42:15 +0100
From: Manfred Spraul <manfred@colorfullife.com>
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To: Patrick McHardy <kaber@trash.net>
CC: Alan Cox <alan@lxorguk.ukuu.org.uk>,
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Subject: Re: PATCH: kmalloc packet slab
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>
>
>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