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Commit 9b0c290e authored Oct 20, 2010 by Eric Dumazet Committed by David S. Miller Oct 21, 2010

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>

parent 7b5edbc4

net/ipv4/fib_hash.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -335,7 +335,8 @@ void fib_table_select_default(struct fib_table *tb,
		if (!next_fi->fib_nh[0].nh_gw \|\|
		next_fi->fib_nh[0].nh_scope != RT_SCOPE_LINK)
		continue;
		fa->fa_state \|= FA_S_ACCESSED;

		fib_alias_accessed(fa);

		if (fi == NULL) {
		if (next_fi != res->fi)

net/ipv4/fib_lookup.h

+7 −0

Original line number	Diff line number	Diff line
		@@ -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,

net/ipv4/fib_semantics.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -901,7 +901,7 @@ int fib_semantic_match(struct list_head head, const struct flowi flp,
		if (fa->fa_scope < flp->fl4_scope)
		continue;

		fa->fa_state \|= FA_S_ACCESSED;
		fib_alias_accessed(fa);

		err = fib_props[fa->fa_type].error;
		if (err == 0) {

net/ipv4/fib_trie.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -1838,7 +1838,8 @@ void fib_table_select_default(struct fib_table *tb,
		if (!next_fi->fib_nh[0].nh_gw \|\|
		next_fi->fib_nh[0].nh_scope != RT_SCOPE_LINK)
		continue;
		fa->fa_state \|= FA_S_ACCESSED;

		fib_alias_accessed(fa);

		if (fi == NULL) {
		if (next_fi != res->fi)