From: Stephen Hemminger <shemminger@vyatta•com>
To: Jesse Brandeburg <jesse.brandeburg@gmail•com>,
Jesper Dangaard Brouer <hawk@diku•dk>
Cc: netdev@vger•kernel.org
Subject: [RFC] skb align patch
Date: Sun, 20 Sep 2009 14:22:12 -0700 [thread overview]
Message-ID: <20090920142212.1106d2a1@s6510> (raw)
Based on the Intel suggestion that PCI-express overhead is
a significant cost.
Would people doing performance please measure the impact of
changing SKB alignment (64 bit only).
--- a/arch/x86/include/asm/system.h 2009-09-20 14:08:40.922346912 -0700
+++ b/arch/x86/include/asm/system.h 2009-09-20 14:14:37.012371200 -0700
@@ -455,4 +455,14 @@ static inline void rdtsc_barrier(void)
alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC);
}
+#ifndef CONFIG_X86_32
+/*
+ * DMA to unaligned address is more expensive than the the
+ * overhead of unaligned CPU access.
+ */
+#define NET_IP_ALIGN 0
+#define NET_SKB_PAD L1_CACHE_BYTES
+#endif
+
+
#endif /* _ASM_X86_SYSTEM_H */
next reply other threads:[~2009-09-20 21:22 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-20 21:22 Stephen Hemminger [this message]
2009-09-21 6:13 ` [RFC] skb align patch Eric Dumazet
2009-09-22 4:30 ` Stephen Hemminger
2009-09-22 3:20 ` Eric Dumazet
2009-09-22 5:23 ` Stephen Hemminger
2009-09-22 5:29 ` David Miller
2009-09-23 5:47 ` Thomas Graf
2009-09-25 22:18 ` Herbert Xu
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