From: Patrick McHardy <kaber@trash.net>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: torvalds@osdl.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Maillist netdev <netdev@oss.sgi.com>
Subject: Re: PATCH: kmalloc packet slab
Date: Mon, 27 Dec 2004 18:17:32 +0100 [thread overview]
Message-ID: <41D043AC.2070203@trash.net> (raw)
In-Reply-To: <1104156983.20944.25.camel@localhost.localdomain>
Alan Cox wrote:
> The networking world runs in 1514 byte packets pretty much all the time.
> This adds a 1620 byte slab for such objects and is one of the internally
> generated Red Hat patches we use on things like Fedora Core 3. Original:
> Arjan van de Ven.
>
> Signed-off-by: Alan Cox <alan@redhat.com>
Why 1620 bytes ? Most drivers allocate packet_size + 2 bytes.
dev_alloc_skb adds another 16 bytes, finally alloc_skb adds
sizeof(struct skb_shared_info). So we get:
(32bit): 1514b + 2b + 16b + 160b = 1692b
(64bit): 1514b + 2b + 16b + 312b = 1844b
On paths using alloc_skb instead of dev_alloc_skb it's 16 bytes
less, but 1620 bytes is still too small for full-sized packets.
Regards
Patrick
next prev parent reply other threads:[~2004-12-27 17:18 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-27 14:16 PATCH: kmalloc packet slab Alan Cox
2004-12-27 17:17 ` Patrick McHardy [this message]
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
-- strict thread matches above, loose matches on Subject: below --
2004-12-27 17:42 Manfred Spraul
2004-12-28 5:59 ` Dave Jones
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