On Thu, May 01, 2014 at 09:44:34AM +0100, Mel Gorman wrote: > If cpusets are not in use then we still check a global variable on every > page allocation. Use jump labels to avoid the overhead. > > Signed-off-by: Mel Gorman <mgor...@suse.de> > --- > include/linux/cpuset.h | 31 +++++++++++++++++++++++++++++++ > kernel/cpuset.c | 8 ++++++-- > mm/page_alloc.c | 3 ++- > 3 files changed, 39 insertions(+), 3 deletions(-) > > diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h > index b19d3dc..2b89e07 100644 > --- a/include/linux/cpuset.h > +++ b/include/linux/cpuset.h > @@ -17,6 +17,35 @@ > > extern int number_of_cpusets; /* How many cpusets are defined in > system? */ > > +#ifdef HAVE_JUMP_LABEL > +extern struct static_key cpusets_enabled_key; > +static inline bool cpusets_enabled(void) > +{ > + return static_key_false(&cpusets_enabled_key); > +} > +#else > +static inline bool cpusets_enabled(void) > +{ > + return number_of_cpusets > 1; > +} > +#endif > + > +static inline void cpuset_inc(void) > +{ > + number_of_cpusets++; > +#ifdef HAVE_JUMP_LABEL > + static_key_slow_inc(&cpusets_enabled_key); > +#endif > +} > + > +static inline void cpuset_dec(void) > +{ > + number_of_cpusets--; > +#ifdef HAVE_JUMP_LABEL > + static_key_slow_dec(&cpusets_enabled_key); > +#endif > +}
Why the HAVE_JUMP_LABEL and number_of_cpusets thing? When !HAVE_JUMP_LABEL the static_key thing reverts to an atomic_t and static_key_false() becomes: return unlikely(atomic_read(&key->enabled) > 0); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/