Messages in this thread | | | Date | Tue, 5 Sep 2023 13:33:57 +0530 | Subject | Re: [PATCH] sched/fair: Add SMT4 group_smt_balance handling | From | Shrikanth Hegde <> |
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On 8/22/23 12:49 AM, Tim Chen wrote: > On Mon, 2023-08-07 at 15:06 +0530, Shrikanth Hegde wrote: >>> >>> From: Tim Chen <tim.c.chen@linux.intel.com> >>> Date: Fri, 14 Jul 2023 16:09:30 -0700 >>> Subject: [PATCH] sched/fair: Add SMT4 group_smt_balance handling >>> >>> For SMT4, any group with more than 2 tasks will be marked as >>> group_smt_balance. Retain the behaviour of group_has_spare by marking >>> the busiest group as the group which has the least number of idle_cpus. >>> >>> Also, handle rounding effect of adding (ncores_local + ncores_busy) >>> when the local is fully idle and busy group has more than 2 tasks. >>> Local group should try to pull at least 1 task in this case. >>> >>> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> >>> --- >>> kernel/sched/fair.c | 18 ++++++++++++++++-- >>> 1 file changed, 16 insertions(+), 2 deletions(-) >>> >>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >>> index a87988327f88..566686c5f2bd 100644 >>> --- a/kernel/sched/fair.c >>> +++ b/kernel/sched/fair.c >>> @@ -9563,7 +9563,7 @@ static inline long sibling_imbalance(struct lb_env *env, >>> imbalance /= ncores_local + ncores_busiest; >>> >>> /* Take advantage of resource in an empty sched group */ >>> - if (imbalance == 0 && local->sum_nr_running == 0 && >>> + if (imbalance <= 1 && local->sum_nr_running == 0 && >>> busiest->sum_nr_running > 1) >>> imbalance = 2; >>> >>> @@ -9751,6 +9751,20 @@ static bool update_sd_pick_busiest(struct lb_env *env, >>> break; >>> >>> case group_smt_balance: >>> + /* no idle cpus on both groups handled by group_fully_busy below */ >>> + if (sgs->idle_cpus != 0 || busiest->idle_cpus != 0) { >>> + if (sgs->idle_cpus > busiest->idle_cpus) >>> + return false; >>> + if (sgs->idle_cpus < busiest->idle_cpus) >>> + return true; >>> + if (sgs->sum_nr_running <= busiest->sum_nr_running) >>> + return false; >>> + else >>> + return true; >>> + } >>> + goto fully_busy; >>> + break; >>> + >>> case group_fully_busy: >>> /* >>> * Select the fully busy group with highest avg_load. In >>> @@ -9763,7 +9777,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, >>> * select the 1st one, except if @sg is composed of SMT >>> * siblings. >>> */ >>> - >>> +fully_busy: >>> if (sgs->avg_load < busiest->avg_load) >>> return false; >>> >> >> Hi Tim, Peter. >> >> group_smt_balance(cluster scheduling), patches are in tip/sched/core. I dont >> see this above patch there yet. Currently as is, this can cause function difference >> in SMT4 systems( such as Power10). >> >> Can we please have the above patch as well in tip/sched/core? >> >> Acked-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com> > > Hi Peter, > > Just back from my long vacation. Wonder if you have any comments on the above patch > for fixing the SMT4 case? > > Tim
Hi Tim, Peter.
are there any concerns with the above patch for fixing the SMT4 case. Currently the behavior is group_smt_balance is set for having even 2 tasks in SMT4, ideally it should be same as the group_has_spare.
The above patch copies the same behavior to group_smt_balance. >
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