From 044aea9b83614948c98564000db07d1d32b2d29b Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 19 May 2011 18:59:47 -0700
Subject: [PATCH] selinux: de-crapify avc cache stat code generation
You can turn off the avc cache stats, but distributions seem to not do
that (perhaps because several performance tuning how-to's talk about the
avc cache statistics).
Which is sad, because the code it generates is truly horrendous, with
the statistics update being sandwitched between get_cpu/put_cpu which in
turn causes preemption disables etc. We're talking ten+ instructions
just to increment a per-cpu variable in some pretty hot code.
Fix the craziness by just using 'this_cpu_inc()' instead. Suddenly we
only need a single 'inc' instruction to increment the statistics. This
is quite noticeable in the incredibly hot avc_has_perm_noaudit()
function (which triggers all the statistics by virtue of doing an
avc_lookup() call).
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
security/selinux/avc.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index 1d027e29ce8d..5971e30e8239 100644
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -38,11 +38,7 @@
#define AVC_CACHE_RECLAIM 16
#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
-#define avc_cache_stats_incr(field) \
-do { \
- per_cpu(avc_cache_stats, get_cpu()).field++; \
- put_cpu(); \
-} while (0)
+#define avc_cache_stats_incr(field) this_cpu_inc(avc_cache_stats.field)
#else
#define avc_cache_stats_incr(field) do {} while (0)
#endif
--
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