From: Manfred Spraul <manfred@colorfullife.com>
To: Patrick McHardy <kaber@trash.net>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: PATCH: kmalloc packet slab
Date: Mon, 27 Dec 2004 18:42:15 +0100 [thread overview]
Message-ID: <41D04977.2040902@colorfullife.com> (raw)
>
>
>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
next reply other threads:[~2004-12-27 17:42 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-27 17:42 Manfred Spraul [this message]
2004-12-28 5:59 ` Dave Jones
-- strict thread matches above, loose matches on Subject: below --
2004-12-27 14:16 Alan Cox
2004-12-27 17:17 ` Patrick McHardy
2004-12-27 22:23 ` David S. Miller
2004-12-27 22:50 ` Valdis.Kletnieks
2004-12-27 22:58 ` David S. Miller
2004-12-28 0:51 ` Alan Cox
2004-12-28 6:01 ` Dave Jones
2004-12-30 18:00 ` Andi Kleen
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