From: Eric Dumazet <eric.dumazet@gmail.com>
To: David Miller <davem@davemloft.net>
Cc: netdev <netdev@vger.kernel.org>, jamal <hadi@cyberus.ca>,
Tom Herbert <therbert@google.com>
Subject: [PATCH net-next-2.6] net: Increase NET_SKB_PAD to 64 bytes
Date: Wed, 05 May 2010 07:24:09 +0200 [thread overview]
Message-ID: <1273037049.2304.7.camel@edumazet-laptop> (raw)
eth_type_trans() & get_rps_cpus() currently need two 64bytes cache lines
in packet to compute rxhash.
Increasing NET_SKB_PAD from 32 to 64 reduces the need to one cache line
only, and makes RPS faster.
NET_IP_ALIGN(2) + ethernet_header(14) + IP_header(20/40) + ports(8)
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 746a652..fe5798b 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1356,9 +1356,12 @@ static inline int skb_network_offset(const struct sk_buff *skb)
*
* Various parts of the networking layer expect at least 32 bytes of
* headroom, you should not reduce this.
+ * With RPS, we raised NET_SKB_PAD to 64 so that get_rps_cpus() fetches span
+ * a 64 bytes aligned block to fit modern (>= 64 bytes) cache line sizes
+ * NET_IP_ALIGN(2) + ethernet_header(14) + IP_header(20/40) + ports(8)
*/
#ifndef NET_SKB_PAD
-#define NET_SKB_PAD 32
+#define NET_SKB_PAD 64
#endif
extern int ___pskb_trim(struct sk_buff *skb, unsigned int len);
next reply other threads:[~2010-05-05 5:24 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-05 5:24 Eric Dumazet [this message]
2010-05-07 5:02 ` [PATCH net-next-2.6] net: Increase NET_SKB_PAD to 64 bytes David Miller
2010-05-07 5:15 ` Eric Dumazet
2010-05-07 5:28 ` [microblaze-uclinux] " John Williams
2010-05-07 6:29 ` David Miller
2010-05-07 7:53 ` Michal Simek
2010-05-07 8:32 ` David Miller
2010-05-07 9:02 ` Michal Simek
2010-05-07 9:48 ` Michal Simek
2010-05-07 9:55 ` Eric Dumazet
2010-05-07 10:09 ` Michal Simek
2010-05-07 10:27 ` Eric Dumazet
2010-05-07 9:56 ` David Miller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1273037049.2304.7.camel@edumazet-laptop \
--to=eric.dumazet@gmail.com \
--cc=davem@davemloft.net \
--cc=hadi@cyberus.ca \
--cc=netdev@vger.kernel.org \
--cc=therbert@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox