On 08/01/2014 12:09 AM, Chris Metcalf wrote: > On 7/31/2014 7:51 AM, Michal Hocko wrote: >> On Thu 31-07-14 11:30:19, Lai Jiangshan wrote: >>> It is suggested that cpumask_var_t and alloc_cpumask_var() should be used >>> instead of struct cpumask. But I don't want to add this complicity nor >>> leave this unwelcome "static struct cpumask has_work;", so I just remove >>> it and use flush_work() to perform on all online drain_work. flush_work() >>> performs very quickly on initialized but unused work item, thus we don't >>> need the struct cpumask has_work for performance. >> Why? Just because there is general recommendation for using >> cpumask_var_t rather than cpumask? >> >> In this particular case cpumask shouldn't matter much as it is static. >> Your code will work as well, but I do not see any strong reason to >> change it just to get rid of cpumask which is not on stack. > > The code uses for_each_cpu with a cpumask to avoid waking cpus that don't > need to do work. This is important for the nohz_full type functionality, > power efficiency, etc. So, nack for this change. > flush_work() on initialized but unused work item just disables irq and fetches work->data to test and restores irq and return. the struct cpumask has_work is just premature optimization. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>