Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1283236

Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own cacheline

Show all headers | View raw

On Thu, Dec 03, 2015 at 09:56:02AM -0800, bsegall@google.com wrote:
> Peter Zijlstra <peterz@infradead.org> writes:

> > @@ -7402,11 +7405,12 @@ void __init sched_init(void)
> >  #endif /* CONFIG_RT_GROUP_SCHED */
> >  
> >  #ifdef CONFIG_CGROUP_SCHED
> > +	task_group_cache = KMEM_CACHE(task_group, 0);
> > +
> >  	list_add(&root_task_group.list, &task_groups);
> >  	INIT_LIST_HEAD(&root_task_group.children);
> >  	INIT_LIST_HEAD(&root_task_group.siblings);
> >  	autogroup_init(&init_task);
> > -
> >  #endif /* CONFIG_CGROUP_SCHED */
> >  
> >  	for_each_possible_cpu(i) {
> > --- a/kernel/sched/sched.h
> > +++ b/kernel/sched/sched.h
> > @@ -248,7 +248,12 @@ struct task_group {
> >  	unsigned long shares;
> >  
> >  #ifdef	CONFIG_SMP
> > -	atomic_long_t load_avg;
> > +	/*
> > +	 * load_avg can be heavily contended at clock tick time, so put
> > +	 * it in its own cacheline separated from the fields above which
> > +	 * will also be accessed at each tick.
> > +	 */
> > +	atomic_long_t load_avg ____cacheline_aligned;
> >  #endif
> >  #endif
> >  
> 
> This loses the cacheline-alignment for task_group, is that ok?

I'm a bit dense (its late) can you spell that out? Did you mean me
killing SLAB_HWCACHE_ALIGN? That should not matter because:

#define KMEM_CACHE(__struct, __flags) kmem_cache_create(#__struct,\
		sizeof(struct __struct), __alignof__(struct __struct),\
		(__flags), NULL)

picks up the alignment explicitly.

And struct task_group having one cacheline aligned member, means that
the alignment of the composite object (the struct proper) must be an
integer multiple of this (typically 1).


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v2 0/3] sched/fair: Reduce contention on tg's load_avg Waiman Long <Waiman.Long@hpe.com> - 2015-12-02 19:50 +0100
  [PATCH v2 1/3] sched/fair: Avoid redundant idle_cpu() call in update_sg_lb_stats() Waiman Long <Waiman.Long@hpe.com> - 2015-12-02 19:50 +0100
  [PATCH v2 3/3] sched/fair: Disable tg load_avg update for root_task_group Waiman Long <Waiman.Long@hpe.com> - 2015-12-02 19:50 +0100
    Re: [PATCH v2 3/3] sched/fair: Disable tg load_avg update for root_task_group bsegall@google.com - 2015-12-02 21:00 +0100
    [tip:sched/core] sched/fair:   Disable the task group load_avg update for the root_task_group tip-bot for Waiman Long <tipbot@zytor.com> - 2015-12-04 13:00 +0100
  [PATCH v2 2/3] sched/fair: Move hot load_avg into its own cacheline Waiman Long <Waiman.Long@hpe.com> - 2015-12-02 19:50 +0100
    Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own cacheline bsegall@google.com - 2015-12-02 21:10 +0100
      Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own cacheline Waiman Long <waiman.long@hpe.com> - 2015-12-03 20:30 +0100
        Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own cacheline bsegall@google.com - 2015-12-03 20:50 +0100
    Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own  cacheline Mike Galbraith <umgwanakikbuti@gmail.com> - 2015-12-03 05:40 +0100
      Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own cacheline Waiman Long <waiman.long@hpe.com> - 2015-12-03 20:40 +0100
        Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own  cacheline Mike Galbraith <umgwanakikbuti@gmail.com> - 2015-12-04 03:10 +0100
          Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own cacheline Waiman Long <waiman.long@hpe.com> - 2015-12-04 21:20 +0100
    Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own  cacheline Peter Zijlstra <peterz@infradead.org> - 2015-12-03 12:00 +0100
      Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own cacheline Waiman Long <waiman.long@hpe.com> - 2015-12-03 20:40 +0100
    Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own  cacheline Peter Zijlstra <peterz@infradead.org> - 2015-12-03 12:20 +0100
      Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own cacheline bsegall@google.com - 2015-12-03 19:10 +0100
        Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own  cacheline Peter Zijlstra <peterz@infradead.org> - 2015-12-03 19:20 +0100
          Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own cacheline bsegall@google.com - 2015-12-03 19:30 +0100
      Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own cacheline Waiman Long <waiman.long@hpe.com> - 2015-12-03 21:00 +0100
        Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own  cacheline Peter Zijlstra <peterz@infradead.org> - 2015-12-03 21:10 +0100
    [tip:sched/core] sched/fair: Move the cache-hot 'load_avg'   variable into its own cacheline tip-bot for Waiman Long <tipbot@zytor.com> - 2015-12-04 13:00 +0100

csiph-web