On 05/03/21 20:25, Song Bao Hua (Barry Song) wrote: >> -----Original Message----- >> From: Valentin Schneider [mailto:[email protected]] >> Sent: Saturday, March 6, 2021 12:49 AM >> To: Song Bao Hua (Barry Song) <[email protected]>; >> [email protected]; [email protected]; [email protected]; >> [email protected]; [email protected]; [email protected]; >> [email protected]; [email protected] >> Cc: [email protected]; [email protected]; Song Bao Hua (Barry >> Song) <[email protected]> >> Subject: Re: [PATCH] sched/topology: remove redundant cpumask_and in >> init_overlap_sched_group >> >> On 05/03/21 11:29, Barry Song wrote: >> > mask is built in build_balance_mask() by for_each_cpu(i, sg_span), so >> > it must be a subset of sched_group_span(sg). >> >> So we should indeed have >> >> cpumask_subset(sched_group_span(sg), mask) >> >> but that doesn't imply >> >> cpumask_first(sched_group_span(sg)) == cpumask_first(mask) >> >> does it? I'm thinking if in your topology of N CPUs, CPUs 0 and N-1 are the >> furthest away, you will most likely hit > > It is true: > cpumask_first(sched_group_span(sg)) != cpumask_first(mask) > > but > > cpumask_first_and(sched_group_span(sg), mask) = cpumask_first(mask) > > since mask is always subset of sched_group_span(sg). >
You're right, I read it the wrong way around, sorry about that. Reviewed-by: Valentin Schneider <[email protected]>
