Messages in this thread Patch in this message | | | Date | Wed, 17 Feb 2010 00:16:49 +0530 | From | Vaidyanathan Srinivasan <> | Subject | Re: [patch] sched: fix SMT scheduler regression in find_busiest_queue() |
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* Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> [2010-02-16 23:55:30]:
> * Peter Zijlstra <peterz@infradead.org> [2010-02-16 18:28:44]: > > > 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 > > ok, will fix the comment.
Thanks for the review, here is the updated patch: --- sched: Fix group_capacity for sched_smt_powersavings
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..4466144 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -2541,6 +2541,21 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu, */ if (prefer_sibling) sgs.group_capacity = min(sgs.group_capacity, 1UL); + /* + * If power savings balance is set at this domain, then + * make capacity equal to number of hardware threads to + * accommodate more tasks until capacity is reached. + */ + else if (sd->flags & SD_POWERSAVINGS_BALANCE) + sgs.group_capacity = + cpumask_weight(sched_group_cpus(group)); + + /* + * The default group_capacity is rounded from sum of + * fractional cpu_powers of sibling hardware threads + * in order to enable fair use of available hardware + * resources. + */ if (local_group) { sds->this_load = sgs.avg_load; @@ -2855,7 +2870,8 @@ 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; }
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