Messages in this thread | | | Subject | Re: [patch] sched: fix SMT scheduler regression in find_busiest_queue() | From | Peter Zijlstra <> | Date | Tue, 16 Feb 2010 18:28:44 +0100 |
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On Tue, 2010-02-16 at 21:29 +0530, Vaidyanathan Srinivasan wrote: > Agreed. Placement control should be handled by SD_PREFER_SIBLING > and SD_POWER_SAVINGS flags. > > --Vaidy > > --- > > sched_smt_powersavings for threaded systems need this fix for > consolidation to sibling threads to work. Since threads have > fractional capacity, group_capacity will turn out to be one > always and not accommodate another task in the sibling thread. > > This fix makes group_capacity a function of cpumask_weight that > will enable the power saving load balancer to pack tasks among > sibling threads and keep more cores idle. > > Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> > > diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c > index 522cf0e..ec3a5c5 100644 > --- a/kernel/sched_fair.c > +++ b/kernel/sched_fair.c > @@ -2538,9 +2538,17 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu, > * In case the child domain prefers tasks go to siblings > * first, lower the group capacity to one so that we'll try > * and move all the excess tasks away.
I prefer a blank line in between two paragraphs, but even better would be to place this comment at the else if site.
> + * If power savings balance is set at this domain, then > + * make capacity equal to number of hardware threads to > + * accomodate more tasks until capacity is reached. The
my spell checker seems to prefer: accommodate
> + * default is fractional capacity for sibling hardware > + * threads for fair use of available hardware resources. > */ > if (prefer_sibling) > sgs.group_capacity = min(sgs.group_capacity, 1UL); > + else if (sd->flags & SD_POWERSAVINGS_BALANCE) > + sgs.group_capacity = > + cpumask_weight(sched_group_cpus(group));
I guess we should apply cpu_active_mask so that we properly deal with offline siblings, except with cpumasks being the beasts they are I see no cheap way to do that.
> if (local_group) { > sds->this_load = sgs.avg_load; > @@ -2855,7 +2863,8 @@ static int need_active_balance(struct sched_domain *sd, int sd_idle, int idle) > !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE)) > return 0; > > - if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP) > + if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP && > + sched_smt_power_savings < POWERSAVINGS_BALANCE_WAKEUP) > return 0; > }
/me still hopes for that unification patch.. :-)
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