Commit 0868e253 authored Apr 22, 2016 by Jiri Benc Committed by David S. Miller Apr 25, 2016

route: move lwtunnel state to a single place



Commit 751a587a ("route: fix breakage after moving lwtunnel state")
moved lwtstate to the end of dst_entry for 32bit archs. This makes it share
the cacheline with __refcnt which had an unkown effect on performance. For
this reason, the pointer was kept in place for 64bit archs.

However, later performance measurements showed this is of no concern. It
turns out that every performance sensitive path that accesses lwtstate
accesses also struct rtable or struct rt6_info which share the same cache
line.

Thus, to get rid of a few #ifdefs, move the field to the end of the struct
also for 64bit.

Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 6a025a50

include/net/dst.h

+1 −4

Original line number	Diff line number	Diff line
		@@ -85,12 +85,11 @@ struct dst_entry {
		#endif

		#ifdef CONFIG_64BIT
		struct lwtunnel_state *lwtstate;
		/*
		* Align __refcnt to a 64 bytes alignment
		* (L1_CACHE_SIZE would be too much)
		*/
		long __pad_to_align_refcnt[1];
		long __pad_to_align_refcnt[2];
		#endif
		/*
		* __refcnt wants to be on a different cache line from
		@@ -99,9 +98,7 @@ struct dst_entry {
		atomic_t __refcnt; /* client references */
		int __use;
		unsigned long lastuse;
		#ifndef CONFIG_64BIT
		struct lwtunnel_state *lwtstate;
		#endif
		union {
		struct dst_entry *next;
		struct rtable __rcu *rt_next;