From: Linus Torvalds Date: Fri, 20 May 2011 01:59:47 +0000 (-0700) Subject: selinux: de-crapify avc cache stat code generation X-Git-Tag: v3.0~761 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=044aea9b83614948c98564000db07d1d32b2d29b;p=platform%2Fkernel%2Flinux-amlogic.git 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 --- diff --git a/security/selinux/avc.c b/security/selinux/avc.c index 1d027e2..5971e30e 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