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From: Steven Sistare <steven.sistare@oracle.com>
To: Valentin Schneider <valentin.schneider@arm.com>,
	mingo@redhat.com, peterz@infradead.org
Cc: subhra.mazumdar@oracle.com, dhaval.giani@oracle.com,
	daniel.m.jordan@oracle.com, pavel.tatashin@microsoft.com,
	matt@codeblueprint.co.uk, umgwanakikbuti@gmail.com,
	riel@redhat.com, jbacik@fb.com, juri.lelli@redhat.com,
	vincent.guittot@linaro.org, quentin.perret@arm.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 03/10] sched/topology: Provide cfs_overload_cpus bitmap
Date: Mon, 19 Nov 2018 12:32:49 -0500	[thread overview]
Message-ID: <2efadddc-ebc0-1cdb-5580-4a9ab5610e61@oracle.com> (raw)
In-Reply-To: <b103563e-fdf3-62a1-473e-cde1cd7e2d5d@arm.com>

On 11/9/2018 12:38 PM, Valentin Schneider wrote:
> Hi Steve,
> 
> On 09/11/2018 12:50, Steve Sistare wrote:
> [...]
>> @@ -482,6 +484,10 @@ static void update_top_cache_domain(int cpu)
>>  	dirty_sched_domain_sysctl(cpu);
>>  	destroy_sched_domains(tmp);
>>  
>> +	sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
>> +	cfs_overload_cpus = (sd ? sd->shared->cfs_overload_cpus : NULL);
>> +	rcu_assign_pointer(rq->cfs_overload_cpus, cfs_overload_cpus);
>> +
> 
> Why not do this in update_top_cache_domain() where we also look for the
> highest SD_SHARE_PKG_RESOURCES and setup shortcut pointers?

My snippet needs rq which is currently referenced in cpu_attach_domain() but
not in update_top_cache_domain().  I could just as easily do it in 
update_top_cache_domain().  Either way is fine with me.

>>  	update_top_cache_domain(cpu);
>>  }
>>  
>> @@ -1619,9 +1625,19 @@ static void __sdt_free(const struct cpumask *cpu_map)
>>  	}
>>  }
>>  
>> +#define ZALLOC_MASK(maskp, nelems, node)				  \
>> +	(!*(maskp) && !zalloc_sparsemask_node(maskp, nelems,		  \
>> +					      SPARSEMASK_DENSITY_DEFAULT, \
>> +					      GFP_KERNEL, node))	  \
>> +
>>  static int sd_llc_alloc(struct sched_domain *sd)
>>  {
>> -	/* Allocate sd->shared data here. Empty for now. */
>> +	struct sched_domain_shared *sds = sd->shared;
>> +	struct cpumask *span = sched_domain_span(sd);
>> +	int nid = cpu_to_node(cpumask_first(span));
>> +
>> +	if (ZALLOC_MASK(&sds->cfs_overload_cpus, nr_cpu_ids, nid))
> 
> Mmm so this is called once on every CPU, but the !*(maskp) check in the
> macro makes it so there is only one allocation per sd_llc_shared.
> 
> I wouldn't mind having that called out in a comment, or having the
> pointer check done explicitly outside of the macro.

OK, will add a comment.  I like the macro because the code is cleaner if/when 
multiple sets are created.

- Steve

  reply	other threads:[~2018-11-19 17:33 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-09 12:50 [PATCH v3 00/10] steal tasks to improve CPU utilization Steve Sistare
2018-11-09 12:50 ` [PATCH v3 01/10] sched: Provide sparsemask, a reduced contention bitmap Steve Sistare
2018-11-27 15:16   ` Steven Sistare
2018-11-28  1:19     ` Omar Sandoval
2018-12-06 16:07       ` Steven Sistare
2018-12-06 18:19         ` Omar Sandoval
2018-11-09 12:50 ` [PATCH v3 02/10] sched/topology: Provide hooks to allocate data shared per LLC Steve Sistare
2018-11-09 12:50 ` [PATCH v3 03/10] sched/topology: Provide cfs_overload_cpus bitmap Steve Sistare
2018-11-09 17:38   ` Valentin Schneider
2018-11-19 17:32     ` Steven Sistare [this message]
2018-11-20 12:52       ` Valentin Schneider
2018-11-12 16:42   ` Valentin Schneider
2018-11-19 17:33     ` Steven Sistare
2018-11-20 12:42       ` Valentin Schneider
2018-11-26 19:06         ` Steven Sistare
2018-12-03 16:56           ` Valentin Schneider
2018-12-06 16:40             ` Steven Sistare
2018-12-06 17:28               ` Valentin Schneider
2018-11-09 12:50 ` [PATCH v3 04/10] sched/fair: Dynamically update cfs_overload_cpus Steve Sistare
2018-11-09 12:50 ` [PATCH v3 05/10] sched/fair: Hoist idle_stamp up from idle_balance Steve Sistare
2018-11-09 19:07   ` Valentin Schneider
2018-11-19 17:31     ` Steven Sistare
2018-11-20 10:24       ` Valentin Schneider
2018-11-09 12:50 ` [PATCH v3 06/10] sched/fair: Generalize the detach_task interface Steve Sistare
2018-11-09 12:50 ` [PATCH v3 07/10] sched/fair: Provide can_migrate_task_llc Steve Sistare
2018-11-09 12:50 ` [PATCH v3 08/10] sched/fair: Steal work from an overloaded CPU when CPU goes idle Steve Sistare
2018-11-09 12:50 ` [PATCH v3 09/10] sched/fair: disable stealing if too many NUMA nodes Steve Sistare
2018-11-09 12:50 ` [PATCH v3 10/10] sched/fair: Provide idle search schedstats Steve Sistare
2018-11-10 17:08   ` kbuild test robot
2018-11-09 15:02 ` hackbench run scripts Steven Sistare

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