Re: [PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
On Sat, Aug 24, 2013 at 03:15:57AM -0700, Paul Turner wrote: > > +static inline void init_sd_lb_stats(struct sd_lb_stats *sds) > > +{ > > + /* > > +* struct sd_lb_stats { > > +* struct sched_group * busiest; // 0 > > 8 > > +* struct sched_group * this;// 8 > > 8 > > +* long unsigned int total_load; //16 > > 8 > > +* long unsigned int total_pwr; //24 > > 8 > > +* long unsigned int avg_load;//32 > > 8 > > +* struct sg_lb_stats { > > +* long unsigned int avg_load;//40 > > 8 > > +* long unsigned int group_load; //48 > > 8 > > +* ... > > +* } busiest_stat; //40 > > 56 > > +* struct sg_lb_stats this_stat; //96 > > 56 > > +* > > +* // size: 152, cachelines: 3, members: 7 > > +* // last cacheline: 24 bytes > > +* }; > > +* > > +* Skimp on the clearing to avoid duplicate work. We can avoid > > clearing > > +* this_stat because update_sg_lb_stats() does a full > > clear/assignment. > > +* We must however clear busiest_stat::avg_load because > > +* update_sd_pick_busiest() reads this before assignment. > > +*/ > > Does gcc seriously not get this right if we just write: > sds->busiest = NULL; > sds->local = NULL; > > > etc.? There's a thought ;-) How about something like this? sds = (struct sd_lb_stats){ .busiest = NULL, .local = NULL, .busiest_stat = { .avg_load = 0, }, }; C99 named initializers should ignore all unmentioned fields, and I think we don't actually touch any of the other fields unless something is set. -- 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/
Re: [PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
On Sat, Aug 24, 2013 at 03:15:57AM -0700, Paul Turner wrote: +static inline void init_sd_lb_stats(struct sd_lb_stats *sds) +{ + /* +* struct sd_lb_stats { +* struct sched_group * busiest; // 0 8 +* struct sched_group * this;// 8 8 +* long unsigned int total_load; //16 8 +* long unsigned int total_pwr; //24 8 +* long unsigned int avg_load;//32 8 +* struct sg_lb_stats { +* long unsigned int avg_load;//40 8 +* long unsigned int group_load; //48 8 +* ... +* } busiest_stat; //40 56 +* struct sg_lb_stats this_stat; //96 56 +* +* // size: 152, cachelines: 3, members: 7 +* // last cacheline: 24 bytes +* }; +* +* Skimp on the clearing to avoid duplicate work. We can avoid clearing +* this_stat because update_sg_lb_stats() does a full clear/assignment. +* We must however clear busiest_stat::avg_load because +* update_sd_pick_busiest() reads this before assignment. +*/ Does gcc seriously not get this right if we just write: sds-busiest = NULL; sds-local = NULL; etc.? There's a thought ;-) How about something like this? sds = (struct sd_lb_stats){ .busiest = NULL, .local = NULL, .busiest_stat = { .avg_load = 0, }, }; C99 named initializers should ignore all unmentioned fields, and I think we don't actually touch any of the other fields unless something is set. -- 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/
Re: [PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
On Mon, Aug 19, 2013 at 9:01 AM, Peter Zijlstra wrote: > We can shrink sg_lb_stats because rq::nr_running is an 'unsigned int' > and cpu numbers are 'int' > > Before: > sgs:/* size: 72, cachelines: 2, members: 10 */ > sds:/* size: 184, cachelines: 3, members: 7 */ > > After: > sgs:/* size: 56, cachelines: 1, members: 10 */ > sds:/* size: 152, cachelines: 3, members: 7 */ > > Further we can avoid clearing all of sds since we do a total > clear/assignment of sg_stats in update_sg_lb_stats() with exception of > busiest_stat.avg_load which is referenced in update_sd_pick_busiest(). > > Signed-off-by: Peter Zijlstra > --- > kernel/sched/fair.c | 42 +++--- > 1 file changed, 35 insertions(+), 7 deletions(-) > > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -4282,12 +4282,12 @@ static unsigned long task_h_load(struct > struct sg_lb_stats { > unsigned long avg_load; /*Avg load across the CPUs of the group */ > unsigned long group_load; /* Total load over the CPUs of the group */ > - unsigned long sum_nr_running; /* Nr tasks running in the group */ > unsigned long sum_weighted_load; /* Weighted load of group's tasks */ > unsigned long load_per_task; > - unsigned long group_capacity; > - unsigned long idle_cpus; > - unsigned long group_weight; > + unsigned int sum_nr_running; /* Nr tasks running in the group */ > + unsigned int group_capacity; > + unsigned int idle_cpus; > + unsigned int group_weight; > int group_imb; /* Is there an imbalance in the group ? */ > int group_has_capacity; /* Is there extra capacity in the group? */ > }; > @@ -4303,10 +4303,38 @@ struct sd_lb_stats { > unsigned long total_pwr;/* Total power of all groups in sd */ > unsigned long avg_load; /* Average load across all groups in sd */ > > - struct sg_lb_stats this_stat; /* Statistics of this group */ > struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */ > + struct sg_lb_stats this_stat; /* Statistics of this group */ > }; > > +static inline void init_sd_lb_stats(struct sd_lb_stats *sds) > +{ > + /* > +* struct sd_lb_stats { > +* struct sched_group * busiest; // 0 8 > +* struct sched_group * this;// 8 8 > +* long unsigned int total_load; //16 8 > +* long unsigned int total_pwr; //24 8 > +* long unsigned int avg_load;//32 8 > +* struct sg_lb_stats { > +* long unsigned int avg_load;//40 8 > +* long unsigned int group_load; //48 8 > +* ... > +* } busiest_stat; //40 56 > +* struct sg_lb_stats this_stat; //96 56 > +* > +* // size: 152, cachelines: 3, members: 7 > +* // last cacheline: 24 bytes > +* }; > +* > +* Skimp on the clearing to avoid duplicate work. We can avoid > clearing > +* this_stat because update_sg_lb_stats() does a full > clear/assignment. > +* We must however clear busiest_stat::avg_load because > +* update_sd_pick_busiest() reads this before assignment. > +*/ Does gcc seriously not get this right if we just write: sds->busiest = NULL; sds->local = NULL; etc.? > + memset(sds, 0, offsetof(struct sd_lb_stats, busiest_stat.group_load)); > +} > + > /** > * get_sd_load_idx - Obtain the load index for a given sched domain. > * @sd: The sched_domain whose load_idx is to be obtained. > @@ -4665,7 +4693,7 @@ static inline void update_sd_lb_stats(st > */ > if (prefer_sibling && !local_group && > sds->this && > sds->this_stat.group_has_capacity) > - sgs->group_capacity = min(sgs->group_capacity, 1UL); > + sgs->group_capacity = min(sgs->group_capacity, 1U); > > /* Now, start updating sd_lb_stats */ > sds->total_load += sgs->group_load; > @@ -4896,7 +4924,7 @@ static struct sched_group *find_busiest_ > struct sg_lb_stats *this, *busiest; > struct sd_lb_stats sds; > > - memset(, 0, sizeof(sds)); > + init_sd_lb_stats(); > > /* > * Compute the various statistics relavent for load balancing at > > -- 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/
Re: [PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
On Mon, Aug 19, 2013 at 9:01 AM, Peter Zijlstra pet...@infradead.org wrote: We can shrink sg_lb_stats because rq::nr_running is an 'unsigned int' and cpu numbers are 'int' Before: sgs:/* size: 72, cachelines: 2, members: 10 */ sds:/* size: 184, cachelines: 3, members: 7 */ After: sgs:/* size: 56, cachelines: 1, members: 10 */ sds:/* size: 152, cachelines: 3, members: 7 */ Further we can avoid clearing all of sds since we do a total clear/assignment of sg_stats in update_sg_lb_stats() with exception of busiest_stat.avg_load which is referenced in update_sd_pick_busiest(). Signed-off-by: Peter Zijlstra pet...@infradead.org --- kernel/sched/fair.c | 42 +++--- 1 file changed, 35 insertions(+), 7 deletions(-) --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4282,12 +4282,12 @@ static unsigned long task_h_load(struct struct sg_lb_stats { unsigned long avg_load; /*Avg load across the CPUs of the group */ unsigned long group_load; /* Total load over the CPUs of the group */ - unsigned long sum_nr_running; /* Nr tasks running in the group */ unsigned long sum_weighted_load; /* Weighted load of group's tasks */ unsigned long load_per_task; - unsigned long group_capacity; - unsigned long idle_cpus; - unsigned long group_weight; + unsigned int sum_nr_running; /* Nr tasks running in the group */ + unsigned int group_capacity; + unsigned int idle_cpus; + unsigned int group_weight; int group_imb; /* Is there an imbalance in the group ? */ int group_has_capacity; /* Is there extra capacity in the group? */ }; @@ -4303,10 +4303,38 @@ struct sd_lb_stats { unsigned long total_pwr;/* Total power of all groups in sd */ unsigned long avg_load; /* Average load across all groups in sd */ - struct sg_lb_stats this_stat; /* Statistics of this group */ struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */ + struct sg_lb_stats this_stat; /* Statistics of this group */ }; +static inline void init_sd_lb_stats(struct sd_lb_stats *sds) +{ + /* +* struct sd_lb_stats { +* struct sched_group * busiest; // 0 8 +* struct sched_group * this;// 8 8 +* long unsigned int total_load; //16 8 +* long unsigned int total_pwr; //24 8 +* long unsigned int avg_load;//32 8 +* struct sg_lb_stats { +* long unsigned int avg_load;//40 8 +* long unsigned int group_load; //48 8 +* ... +* } busiest_stat; //40 56 +* struct sg_lb_stats this_stat; //96 56 +* +* // size: 152, cachelines: 3, members: 7 +* // last cacheline: 24 bytes +* }; +* +* Skimp on the clearing to avoid duplicate work. We can avoid clearing +* this_stat because update_sg_lb_stats() does a full clear/assignment. +* We must however clear busiest_stat::avg_load because +* update_sd_pick_busiest() reads this before assignment. +*/ Does gcc seriously not get this right if we just write: sds-busiest = NULL; sds-local = NULL; etc.? + memset(sds, 0, offsetof(struct sd_lb_stats, busiest_stat.group_load)); +} + /** * get_sd_load_idx - Obtain the load index for a given sched domain. * @sd: The sched_domain whose load_idx is to be obtained. @@ -4665,7 +4693,7 @@ static inline void update_sd_lb_stats(st */ if (prefer_sibling !local_group sds-this sds-this_stat.group_has_capacity) - sgs-group_capacity = min(sgs-group_capacity, 1UL); + sgs-group_capacity = min(sgs-group_capacity, 1U); /* Now, start updating sd_lb_stats */ sds-total_load += sgs-group_load; @@ -4896,7 +4924,7 @@ static struct sched_group *find_busiest_ struct sg_lb_stats *this, *busiest; struct sd_lb_stats sds; - memset(sds, 0, sizeof(sds)); + init_sd_lb_stats(sds); /* * Compute the various statistics relavent for load balancing at -- 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/
Re: [PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
On Wed, Aug 21, 2013 at 11:20:02AM +0900, Joonsoo Kim wrote: > > With below change, we can simply do 'offsetof(struct sd_lb_stats, > > busiest_stat)'. > > > > @@ -4546,7 +4546,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, > >struct sched_group *sg, > >struct sg_lb_stats *sgs) > > { > > - if (sgs->avg_load <= sds->busiest_stat.avg_load) > > + if (!sds->busiest && sgs->avg_load <= sds->busiest_stat.avg_load) > > return false; > > > > if (sgs->sum_nr_running > sgs->group_capacity) > > > > Sorry, instead of !sds->busiest, it should be sds->busiest. :) Of course ;-) However I'm not sure which I prefer.. adding this extra condition or having the initialization extra tricky. I'll sit on it a little longer. -- 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/
Re: [PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
On Wed, Aug 21, 2013 at 11:08:29AM +0900, Joonsoo Kim wrote: > On Mon, Aug 19, 2013 at 06:01:02PM +0200, Peter Zijlstra wrote: > > +static inline void init_sd_lb_stats(struct sd_lb_stats *sds) > > +{ > > + /* > > +* struct sd_lb_stats { > > +* struct sched_group * busiest; // 0 8 > > +* struct sched_group * this;// 8 8 > > +* long unsigned int total_load; //16 8 > > +* long unsigned int total_pwr; //24 8 > > +* long unsigned int avg_load;//32 8 > > +* struct sg_lb_stats { > > +* long unsigned int avg_load;//40 8 > > +* long unsigned int group_load; //48 8 > > +* ... > > +* } busiest_stat; //40 56 > > +* struct sg_lb_stats this_stat; //96 56 > > +* > > +* // size: 152, cachelines: 3, members: 7 > > +* // last cacheline: 24 bytes > > +* }; > > +* > > +* Skimp on the clearing to avoid duplicate work. We can avoid clearing > > +* this_stat because update_sg_lb_stats() does a full clear/assignment. > > +* We must however clear busiest_stat::avg_load because > > +* update_sd_pick_busiest() reads this before assignment. > > +*/ > > + memset(sds, 0, offsetof(struct sd_lb_stats, busiest_stat.group_load)); > > Hello, Peter. > > IMHO, this is so tricky. Agreed, hence the somewhat elaborate comment :/ > With below change, we can simply do 'offsetof(struct sd_lb_stats, > busiest_stat)'. > > @@ -4546,7 +4546,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, >struct sched_group *sg, >struct sg_lb_stats *sgs) > { > - if (sgs->avg_load <= sds->busiest_stat.avg_load) > + if (!sds->busiest && sgs->avg_load <= sds->busiest_stat.avg_load) > return false; > > if (sgs->sum_nr_running > sgs->group_capacity) Indeed, thanks! -- 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/
Re: [PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
On Wed, Aug 21, 2013 at 11:08:29AM +0900, Joonsoo Kim wrote: On Mon, Aug 19, 2013 at 06:01:02PM +0200, Peter Zijlstra wrote: +static inline void init_sd_lb_stats(struct sd_lb_stats *sds) +{ + /* +* struct sd_lb_stats { +* struct sched_group * busiest; // 0 8 +* struct sched_group * this;// 8 8 +* long unsigned int total_load; //16 8 +* long unsigned int total_pwr; //24 8 +* long unsigned int avg_load;//32 8 +* struct sg_lb_stats { +* long unsigned int avg_load;//40 8 +* long unsigned int group_load; //48 8 +* ... +* } busiest_stat; //40 56 +* struct sg_lb_stats this_stat; //96 56 +* +* // size: 152, cachelines: 3, members: 7 +* // last cacheline: 24 bytes +* }; +* +* Skimp on the clearing to avoid duplicate work. We can avoid clearing +* this_stat because update_sg_lb_stats() does a full clear/assignment. +* We must however clear busiest_stat::avg_load because +* update_sd_pick_busiest() reads this before assignment. +*/ + memset(sds, 0, offsetof(struct sd_lb_stats, busiest_stat.group_load)); Hello, Peter. IMHO, this is so tricky. Agreed, hence the somewhat elaborate comment :/ With below change, we can simply do 'offsetof(struct sd_lb_stats, busiest_stat)'. @@ -4546,7 +4546,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, struct sched_group *sg, struct sg_lb_stats *sgs) { - if (sgs-avg_load = sds-busiest_stat.avg_load) + if (!sds-busiest sgs-avg_load = sds-busiest_stat.avg_load) return false; if (sgs-sum_nr_running sgs-group_capacity) Indeed, thanks! -- 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/
Re: [PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
On Wed, Aug 21, 2013 at 11:20:02AM +0900, Joonsoo Kim wrote: With below change, we can simply do 'offsetof(struct sd_lb_stats, busiest_stat)'. @@ -4546,7 +4546,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, struct sched_group *sg, struct sg_lb_stats *sgs) { - if (sgs-avg_load = sds-busiest_stat.avg_load) + if (!sds-busiest sgs-avg_load = sds-busiest_stat.avg_load) return false; if (sgs-sum_nr_running sgs-group_capacity) Sorry, instead of !sds-busiest, it should be sds-busiest. :) Of course ;-) However I'm not sure which I prefer.. adding this extra condition or having the initialization extra tricky. I'll sit on it a little longer. -- 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/
Re: [PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
On Wed, Aug 21, 2013 at 11:08:29AM +0900, Joonsoo Kim wrote: > On Mon, Aug 19, 2013 at 06:01:02PM +0200, Peter Zijlstra wrote: > > +static inline void init_sd_lb_stats(struct sd_lb_stats *sds) > > +{ > > + /* > > +* struct sd_lb_stats { > > +* struct sched_group * busiest; // 0 8 > > +* struct sched_group * this;// 8 8 > > +* long unsigned int total_load; //16 8 > > +* long unsigned int total_pwr; //24 8 > > +* long unsigned int avg_load;//32 8 > > +* struct sg_lb_stats { > > +* long unsigned int avg_load;//40 8 > > +* long unsigned int group_load; //48 8 > > +* ... > > +* } busiest_stat; //40 56 > > +* struct sg_lb_stats this_stat; //96 56 > > +* > > +* // size: 152, cachelines: 3, members: 7 > > +* // last cacheline: 24 bytes > > +* }; > > +* > > +* Skimp on the clearing to avoid duplicate work. We can avoid clearing > > +* this_stat because update_sg_lb_stats() does a full clear/assignment. > > +* We must however clear busiest_stat::avg_load because > > +* update_sd_pick_busiest() reads this before assignment. > > +*/ > > + memset(sds, 0, offsetof(struct sd_lb_stats, busiest_stat.group_load)); > > Hello, Peter. > > IMHO, this is so tricky. > With below change, we can simply do 'offsetof(struct sd_lb_stats, > busiest_stat)'. > > @@ -4546,7 +4546,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, >struct sched_group *sg, >struct sg_lb_stats *sgs) > { > - if (sgs->avg_load <= sds->busiest_stat.avg_load) > + if (!sds->busiest && sgs->avg_load <= sds->busiest_stat.avg_load) > return false; > > if (sgs->sum_nr_running > sgs->group_capacity) > Sorry, instead of !sds->busiest, it should be sds->busiest. :) Thanks. -- 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/
Re: [PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
On Mon, Aug 19, 2013 at 06:01:02PM +0200, Peter Zijlstra wrote: > +static inline void init_sd_lb_stats(struct sd_lb_stats *sds) > +{ > + /* > + * struct sd_lb_stats { > + * struct sched_group * busiest; // 0 8 > + * struct sched_group * this;// 8 8 > + * long unsigned int total_load; //16 8 > + * long unsigned int total_pwr; //24 8 > + * long unsigned int avg_load;//32 8 > + * struct sg_lb_stats { > + * long unsigned int avg_load;//40 8 > + * long unsigned int group_load; //48 8 > + * ... > + * } busiest_stat; //40 56 > + * struct sg_lb_stats this_stat; //96 56 > + * > + * // size: 152, cachelines: 3, members: 7 > + * // last cacheline: 24 bytes > + * }; > + * > + * Skimp on the clearing to avoid duplicate work. We can avoid clearing > + * this_stat because update_sg_lb_stats() does a full clear/assignment. > + * We must however clear busiest_stat::avg_load because > + * update_sd_pick_busiest() reads this before assignment. > + */ > + memset(sds, 0, offsetof(struct sd_lb_stats, busiest_stat.group_load)); Hello, Peter. IMHO, this is so tricky. With below change, we can simply do 'offsetof(struct sd_lb_stats, busiest_stat)'. @@ -4546,7 +4546,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, struct sched_group *sg, struct sg_lb_stats *sgs) { - if (sgs->avg_load <= sds->busiest_stat.avg_load) + if (!sds->busiest && sgs->avg_load <= sds->busiest_stat.avg_load) return false; if (sgs->sum_nr_running > sgs->group_capacity) Thanks. -- 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/
Re: [PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
On Mon, Aug 19, 2013 at 06:01:02PM +0200, Peter Zijlstra wrote: +static inline void init_sd_lb_stats(struct sd_lb_stats *sds) +{ + /* + * struct sd_lb_stats { + * struct sched_group * busiest; // 0 8 + * struct sched_group * this;// 8 8 + * long unsigned int total_load; //16 8 + * long unsigned int total_pwr; //24 8 + * long unsigned int avg_load;//32 8 + * struct sg_lb_stats { + * long unsigned int avg_load;//40 8 + * long unsigned int group_load; //48 8 + * ... + * } busiest_stat; //40 56 + * struct sg_lb_stats this_stat; //96 56 + * + * // size: 152, cachelines: 3, members: 7 + * // last cacheline: 24 bytes + * }; + * + * Skimp on the clearing to avoid duplicate work. We can avoid clearing + * this_stat because update_sg_lb_stats() does a full clear/assignment. + * We must however clear busiest_stat::avg_load because + * update_sd_pick_busiest() reads this before assignment. + */ + memset(sds, 0, offsetof(struct sd_lb_stats, busiest_stat.group_load)); Hello, Peter. IMHO, this is so tricky. With below change, we can simply do 'offsetof(struct sd_lb_stats, busiest_stat)'. @@ -4546,7 +4546,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, struct sched_group *sg, struct sg_lb_stats *sgs) { - if (sgs-avg_load = sds-busiest_stat.avg_load) + if (!sds-busiest sgs-avg_load = sds-busiest_stat.avg_load) return false; if (sgs-sum_nr_running sgs-group_capacity) Thanks. -- 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/
Re: [PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
On Wed, Aug 21, 2013 at 11:08:29AM +0900, Joonsoo Kim wrote: On Mon, Aug 19, 2013 at 06:01:02PM +0200, Peter Zijlstra wrote: +static inline void init_sd_lb_stats(struct sd_lb_stats *sds) +{ + /* +* struct sd_lb_stats { +* struct sched_group * busiest; // 0 8 +* struct sched_group * this;// 8 8 +* long unsigned int total_load; //16 8 +* long unsigned int total_pwr; //24 8 +* long unsigned int avg_load;//32 8 +* struct sg_lb_stats { +* long unsigned int avg_load;//40 8 +* long unsigned int group_load; //48 8 +* ... +* } busiest_stat; //40 56 +* struct sg_lb_stats this_stat; //96 56 +* +* // size: 152, cachelines: 3, members: 7 +* // last cacheline: 24 bytes +* }; +* +* Skimp on the clearing to avoid duplicate work. We can avoid clearing +* this_stat because update_sg_lb_stats() does a full clear/assignment. +* We must however clear busiest_stat::avg_load because +* update_sd_pick_busiest() reads this before assignment. +*/ + memset(sds, 0, offsetof(struct sd_lb_stats, busiest_stat.group_load)); Hello, Peter. IMHO, this is so tricky. With below change, we can simply do 'offsetof(struct sd_lb_stats, busiest_stat)'. @@ -4546,7 +4546,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, struct sched_group *sg, struct sg_lb_stats *sgs) { - if (sgs-avg_load = sds-busiest_stat.avg_load) + if (!sds-busiest sgs-avg_load = sds-busiest_stat.avg_load) return false; if (sgs-sum_nr_running sgs-group_capacity) Sorry, instead of !sds-busiest, it should be sds-busiest. :) Thanks. -- 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/
[PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
We can shrink sg_lb_stats because rq::nr_running is an 'unsigned int' and cpu numbers are 'int' Before: sgs:/* size: 72, cachelines: 2, members: 10 */ sds:/* size: 184, cachelines: 3, members: 7 */ After: sgs:/* size: 56, cachelines: 1, members: 10 */ sds:/* size: 152, cachelines: 3, members: 7 */ Further we can avoid clearing all of sds since we do a total clear/assignment of sg_stats in update_sg_lb_stats() with exception of busiest_stat.avg_load which is referenced in update_sd_pick_busiest(). Signed-off-by: Peter Zijlstra --- kernel/sched/fair.c | 42 +++--- 1 file changed, 35 insertions(+), 7 deletions(-) --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4282,12 +4282,12 @@ static unsigned long task_h_load(struct struct sg_lb_stats { unsigned long avg_load; /*Avg load across the CPUs of the group */ unsigned long group_load; /* Total load over the CPUs of the group */ - unsigned long sum_nr_running; /* Nr tasks running in the group */ unsigned long sum_weighted_load; /* Weighted load of group's tasks */ unsigned long load_per_task; - unsigned long group_capacity; - unsigned long idle_cpus; - unsigned long group_weight; + unsigned int sum_nr_running; /* Nr tasks running in the group */ + unsigned int group_capacity; + unsigned int idle_cpus; + unsigned int group_weight; int group_imb; /* Is there an imbalance in the group ? */ int group_has_capacity; /* Is there extra capacity in the group? */ }; @@ -4303,10 +4303,38 @@ struct sd_lb_stats { unsigned long total_pwr;/* Total power of all groups in sd */ unsigned long avg_load; /* Average load across all groups in sd */ - struct sg_lb_stats this_stat; /* Statistics of this group */ struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */ + struct sg_lb_stats this_stat; /* Statistics of this group */ }; +static inline void init_sd_lb_stats(struct sd_lb_stats *sds) +{ + /* +* struct sd_lb_stats { +* struct sched_group * busiest; // 0 8 +* struct sched_group * this;// 8 8 +* long unsigned int total_load; //16 8 +* long unsigned int total_pwr; //24 8 +* long unsigned int avg_load;//32 8 +* struct sg_lb_stats { +* long unsigned int avg_load;//40 8 +* long unsigned int group_load; //48 8 +* ... +* } busiest_stat; //40 56 +* struct sg_lb_stats this_stat; //96 56 +* +* // size: 152, cachelines: 3, members: 7 +* // last cacheline: 24 bytes +* }; +* +* Skimp on the clearing to avoid duplicate work. We can avoid clearing +* this_stat because update_sg_lb_stats() does a full clear/assignment. +* We must however clear busiest_stat::avg_load because +* update_sd_pick_busiest() reads this before assignment. +*/ + memset(sds, 0, offsetof(struct sd_lb_stats, busiest_stat.group_load)); +} + /** * get_sd_load_idx - Obtain the load index for a given sched domain. * @sd: The sched_domain whose load_idx is to be obtained. @@ -4665,7 +4693,7 @@ static inline void update_sd_lb_stats(st */ if (prefer_sibling && !local_group && sds->this && sds->this_stat.group_has_capacity) - sgs->group_capacity = min(sgs->group_capacity, 1UL); + sgs->group_capacity = min(sgs->group_capacity, 1U); /* Now, start updating sd_lb_stats */ sds->total_load += sgs->group_load; @@ -4896,7 +4924,7 @@ static struct sched_group *find_busiest_ struct sg_lb_stats *this, *busiest; struct sd_lb_stats sds; - memset(, 0, sizeof(sds)); + init_sd_lb_stats(); /* * Compute the various statistics relavent for load balancing at -- 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/
[PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games
We can shrink sg_lb_stats because rq::nr_running is an 'unsigned int' and cpu numbers are 'int' Before: sgs:/* size: 72, cachelines: 2, members: 10 */ sds:/* size: 184, cachelines: 3, members: 7 */ After: sgs:/* size: 56, cachelines: 1, members: 10 */ sds:/* size: 152, cachelines: 3, members: 7 */ Further we can avoid clearing all of sds since we do a total clear/assignment of sg_stats in update_sg_lb_stats() with exception of busiest_stat.avg_load which is referenced in update_sd_pick_busiest(). Signed-off-by: Peter Zijlstra pet...@infradead.org --- kernel/sched/fair.c | 42 +++--- 1 file changed, 35 insertions(+), 7 deletions(-) --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4282,12 +4282,12 @@ static unsigned long task_h_load(struct struct sg_lb_stats { unsigned long avg_load; /*Avg load across the CPUs of the group */ unsigned long group_load; /* Total load over the CPUs of the group */ - unsigned long sum_nr_running; /* Nr tasks running in the group */ unsigned long sum_weighted_load; /* Weighted load of group's tasks */ unsigned long load_per_task; - unsigned long group_capacity; - unsigned long idle_cpus; - unsigned long group_weight; + unsigned int sum_nr_running; /* Nr tasks running in the group */ + unsigned int group_capacity; + unsigned int idle_cpus; + unsigned int group_weight; int group_imb; /* Is there an imbalance in the group ? */ int group_has_capacity; /* Is there extra capacity in the group? */ }; @@ -4303,10 +4303,38 @@ struct sd_lb_stats { unsigned long total_pwr;/* Total power of all groups in sd */ unsigned long avg_load; /* Average load across all groups in sd */ - struct sg_lb_stats this_stat; /* Statistics of this group */ struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */ + struct sg_lb_stats this_stat; /* Statistics of this group */ }; +static inline void init_sd_lb_stats(struct sd_lb_stats *sds) +{ + /* +* struct sd_lb_stats { +* struct sched_group * busiest; // 0 8 +* struct sched_group * this;// 8 8 +* long unsigned int total_load; //16 8 +* long unsigned int total_pwr; //24 8 +* long unsigned int avg_load;//32 8 +* struct sg_lb_stats { +* long unsigned int avg_load;//40 8 +* long unsigned int group_load; //48 8 +* ... +* } busiest_stat; //40 56 +* struct sg_lb_stats this_stat; //96 56 +* +* // size: 152, cachelines: 3, members: 7 +* // last cacheline: 24 bytes +* }; +* +* Skimp on the clearing to avoid duplicate work. We can avoid clearing +* this_stat because update_sg_lb_stats() does a full clear/assignment. +* We must however clear busiest_stat::avg_load because +* update_sd_pick_busiest() reads this before assignment. +*/ + memset(sds, 0, offsetof(struct sd_lb_stats, busiest_stat.group_load)); +} + /** * get_sd_load_idx - Obtain the load index for a given sched domain. * @sd: The sched_domain whose load_idx is to be obtained. @@ -4665,7 +4693,7 @@ static inline void update_sd_lb_stats(st */ if (prefer_sibling !local_group sds-this sds-this_stat.group_has_capacity) - sgs-group_capacity = min(sgs-group_capacity, 1UL); + sgs-group_capacity = min(sgs-group_capacity, 1U); /* Now, start updating sd_lb_stats */ sds-total_load += sgs-group_load; @@ -4896,7 +4924,7 @@ static struct sched_group *find_busiest_ struct sg_lb_stats *this, *busiest; struct sd_lb_stats sds; - memset(sds, 0, sizeof(sds)); + init_sd_lb_stats(sds); /* * Compute the various statistics relavent for load balancing at -- 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/