On Mon 24-08-15 13:09:43, Mel Gorman wrote: > David Rientjes correctly pointed out that the "root cpuset may not exclude > mems on the system so, even if mounted, there's no need to check or be > worried about concurrent change when there is only one cpuset".
Hmm, but cpuset_inc() is called only from cpuset_css_online and only when it is called with non-NULL css->parent AFAICS. This means that the static key should be still false after the root cpuset is created. > The three checks for cpusets_enabled() care whether a cpuset exists that > can limit memory, not that cpuset is enabled as such. This patch replaces > cpusets_enabled() with cpusets_mems_enabled() which checks if at least one > cpuset exists that can limit memory and updates the appropriate call sites. > > Signed-off-by: Mel Gorman <[email protected]> > --- > include/linux/cpuset.h | 16 +++++++++------- > mm/page_alloc.c | 2 +- > 2 files changed, 10 insertions(+), 8 deletions(-) > > diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h > index 6eb27cb480b7..1e823870987e 100644 > --- a/include/linux/cpuset.h > +++ b/include/linux/cpuset.h > @@ -17,10 +17,6 @@ > #ifdef CONFIG_CPUSETS > > extern struct static_key cpusets_enabled_key; > -static inline bool cpusets_enabled(void) > -{ > - return static_key_false(&cpusets_enabled_key); > -} > > static inline int nr_cpusets(void) > { > @@ -28,6 +24,12 @@ static inline int nr_cpusets(void) > return static_key_count(&cpusets_enabled_key) + 1; > } > > +/* Returns true if a cpuset exists that can set cpuset.mems */ > +static inline bool cpusets_mems_enabled(void) > +{ > + return nr_cpusets() > 1; > +} > + > static inline void cpuset_inc(void) > { > static_key_slow_inc(&cpusets_enabled_key); > @@ -104,7 +106,7 @@ extern void cpuset_print_task_mems_allowed(struct > task_struct *p); > */ > static inline unsigned int read_mems_allowed_begin(void) > { > - if (!cpusets_enabled()) > + if (!cpusets_mems_enabled()) > return 0; > > return read_seqcount_begin(¤t->mems_allowed_seq); > @@ -118,7 +120,7 @@ static inline unsigned int read_mems_allowed_begin(void) > */ > static inline bool read_mems_allowed_retry(unsigned int seq) > { > - if (!cpusets_enabled()) > + if (!cpusets_mems_enabled()) > return false; > > return read_seqcount_retry(¤t->mems_allowed_seq, seq); > @@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask) > > #else /* !CONFIG_CPUSETS */ > > -static inline bool cpusets_enabled(void) { return false; } > +static inline bool cpusets_mems_enabled(void) { return false; } > > static inline int cpuset_init(void) { return 0; } > static inline void cpuset_init_smp(void) {} > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 62ae28d8ae8d..2c1c3bf54d15 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int > order, int alloc_flags, > if (IS_ENABLED(CONFIG_NUMA) && zlc_active && > !zlc_zone_worth_trying(zonelist, z, allowednodes)) > continue; > - if (cpusets_enabled() && > + if (cpusets_mems_enabled() && > (alloc_flags & ALLOC_CPUSET) && > !cpuset_zone_allowed(zone, gfp_mask)) > continue; > -- > 2.4.6 -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
