| To: | Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> |
|---|---|
| Subject: | Re: PATCH: kmalloc packet slab |
| From: | Patrick McHardy <kaber@xxxxxxxxx> |
| Date: | Mon, 27 Dec 2004 18:17:32 +0100 |
| Cc: | torvalds@xxxxxxxx, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Maillist netdev <netdev@xxxxxxxxxxx> |
| In-reply-to: | <1104156983.20944.25.camel@xxxxxxxxxxxxxxxxxxxxx> |
| References: | <1104156983.20944.25.camel@xxxxxxxxxxxxxxxxxxxxx> |
| Sender: | netdev-bounce@xxxxxxxxxxx |
| User-agent: | Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.6) Gecko/20040413 Debian/1.6-5 |
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@xxxxxxxxxx> 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 |
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