Re: [PATCH 3/4] workqueue: Create low-level unbound workqueues cpumask

[Lai Jiangshan <laijs@cn.fujitsu.com>]

On 03/14/2015 07:49 AM, Kevin Hilman wrote:
> Lai Jiangshan <laijs@cn.fujitsu.com> writes:
> 
>> From: Frederic Weisbecker <fweisbec@gmail.com>
>>
>> Create a cpumask that limit the affinity of all unbound workqueues.
>> This cpumask is controlled though a file at the root of the workqueue
>> sysfs directory.
>>
>> It works on a lower-level than the per WQ_SYSFS workqueues cpumask files
>> such that the effective cpumask applied for a given unbound workqueue is
>> the intersection of /sys/devices/virtual/workqueue/$WORKQUEUE/cpumask and
>> the new /sys/devices/virtual/workqueue/cpumask_unbounds file.
>>
>> This patch implements the basic infrastructure and the read interface.
>> cpumask_unbounds is initially set to cpu_possible_mask.
>>
>> Cc: Christoph Lameter <cl@linux.com>
>> Cc: Kevin Hilman <khilman@linaro.org>
>> Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
>> Cc: Mike Galbraith <bitbucket@online.de>
>> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>> Cc: Tejun Heo <tj@kernel.org>
>> Cc: Viresh Kumar <viresh.kumar@linaro.org>
>> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
>> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> 
> [...]
> 
>> @@ -5094,6 +5116,9 @@ static int __init init_workqueues(void)
>>  
>>  	WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
>>  
>> +	BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
>> +	cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
>> +
> 
> As I mentioned in an earlier discussion[1], I still think this could
> default too the housekeeping CPUs in the NO_HZ_FULL case:
> 
> #ifdef CONFIG_NO_HZ_FULL
> 	cpumask_complement(wq_unbound_cpumask, tick_nohz_full_mask);


No, the default/booted wq_unbound_cpumask should be cpu_possible_mask.

> #else
> 	cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
> #endif
> 
> But that could also be left to a future optimization as well.
> 
> Kevin
> 
> [1] https://lkml.org/lkml/2014/2/14/666
> .
>