net: force dst_default_metrics to const section
While investigating on network performance problems, I found this little
gem :
$ nm -v vmlinux | grep -1 dst_default_metrics
ffffffff82736540 b busy.46605
ffffffff82736560 B dst_default_metrics
ffffffff82736598 b dst_busy_list
Apparently, declaring a const array without initializer put it in
(writeable) bss section, in middle of possibly often dirtied cache
lines.
Since we really want dst_default_metrics be const to avoid any possible
false sharing and catch any buggy writes, I force a null initializer.
ffffffff818a4c20 R dst_default_metrics
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/dst.h b/include/net/dst.h
index baf5978..621e351 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -110,7 +110,7 @@
};
extern u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old);
-extern const u32 dst_default_metrics[RTAX_MAX];
+extern const u32 dst_default_metrics[];
#define DST_METRICS_READ_ONLY 0x1UL
#define __DST_METRICS_PTR(Y) \