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yaml --- r: 202963 b: refs/heads/master c: 5933dd2 h: refs/heads/master i: 202961: 00c160b 202959: a86db5e v: v3
git-mirror · Jun 16, 2010 · c5a4ae2 · c5a4ae2
1 parent 79e2fb9
commit c5a4ae2
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Showing 4 changed files with 6 additions and 10 deletions.
diff --git a/[refs] b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a95d8c88bea0c93505e1d143d075f112be2b25e3
+refs/heads/master: 5933dd2f028cdcbb4b3169dca594324704ba10ae
diff --git a/trunk/arch/microblaze/include/asm/system.h b/trunk/arch/microblaze/include/asm/system.h
@@ -101,10 +101,7 @@ extern struct dentry *of_debugfs_root;
  * MicroBlaze doesn't handle unaligned accesses in hardware.
  *
  * Based on this we force the IP header alignment in network drivers.
- * We also modify NET_SKB_PAD to be a cacheline in size, thus maintaining
- * cacheline alignment of buffers.
  */
 #define NET_IP_ALIGN	2
-#define NET_SKB_PAD	L1_CACHE_BYTES
 
 #endif /* _ASM_MICROBLAZE_SYSTEM_H */
diff --git a/trunk/arch/powerpc/include/asm/system.h b/trunk/arch/powerpc/include/asm/system.h
@@ -515,11 +515,8 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
  * powers of 2 writes until it reaches sufficient alignment).
  *
  * Based on this we disable the IP header alignment in network drivers.
- * We also modify NET_SKB_PAD to be a cacheline in size, thus maintaining
- * cacheline alignment of buffers.
  */
 #define NET_IP_ALIGN	0
-#define NET_SKB_PAD	L1_CACHE_BYTES
 
 #define cmpxchg64(ptr, o, n)						\
   ({									\

diff --git a/trunk/include/linux/skbuff.h b/trunk/include/linux/skbuff.h
@@ -1414,12 +1414,14 @@ 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
+ *
+ * Using max(32, L1_CACHE_BYTES) makes sense (especially with RPS)
+ * to reduce average number of cache lines per packet.
+ * get_rps_cpus() for example only access one 64 bytes aligned block :
  * NET_IP_ALIGN(2) + ethernet_header(14) + IP_header(20/40) + ports(8)
  */
 #ifndef NET_SKB_PAD
-#define NET_SKB_PAD	64
+#define NET_SKB_PAD	max(32, L1_CACHE_BYTES)
 #endif
 
 extern int ___pskb_trim(struct sk_buff *skb, unsigned int len);