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authorEric Dumazet <eric.dumazet@gmail.com>2010-10-20 22:03:38 +0000
committerDavid S. Miller <davem@davemloft.net>2010-10-21 03:09:41 -0700
commit9b0c290e78d667e6a483bde8c7cef7dd15f49017 (patch)
treeed68f6cbcc9a512106217694b16a846147cdf54a /net/ipv4/fib_lookup.h
parent7b5edbc4cfe2297b0915adea5aa1eafcafadbf06 (diff)
downloadlinux-9b0c290e78d667e6a483bde8c7cef7dd15f49017.tar.bz2
fib: introduce fib_alias_accessed() helper
Perf tools session at NFWS 2010 pointed out a false sharing on struct fib_alias that can be avoided pretty easily, if we set FA_S_ACCESSED bit only if needed (ie : not already set) Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/fib_lookup.h')
-rw-r--r--net/ipv4/fib_lookup.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/net/ipv4/fib_lookup.h b/net/ipv4/fib_lookup.h
index 5072d8effd5d..a29edf2219c8 100644
--- a/net/ipv4/fib_lookup.h
+++ b/net/ipv4/fib_lookup.h
@@ -17,6 +17,13 @@ struct fib_alias {
#define FA_S_ACCESSED 0x01
+/* Dont write on fa_state unless needed, to keep it shared on all cpus */
+static inline void fib_alias_accessed(struct fib_alias *fa)
+{
+ if (!(fa->fa_state & FA_S_ACCESSED))
+ fa->fa_state |= FA_S_ACCESSED;
+}
+
/* Exported by fib_semantics.c */
extern int fib_semantic_match(struct list_head *head,
const struct flowi *flp,