Messages in this thread Patch in this message | | | Subject | Re: [PATCH] sched/fair: Add SMT4 group_smt_balance handling | From | Tim Chen <> | Date | Thu, 27 Jul 2023 06:32:44 -0700 |
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On Wed, 2023-07-26 at 20:11 -0700, Tim Chen wrote: > On Mon, 2023-07-17 at 20:28 +0530, Shrikanth Hegde wrote: > > From: Tim Chen <tim.c.chen@linux.intel.com> > > > > 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. > > > > Originally-by: Tim Chen <tim.c.chen@linux.intel.com> > > Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> > > Signed-off-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com> > > --- > > kernel/sched/fair.c | 13 ++++++++++++- > > 1 file changed, 12 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index 932e7b78894a..9502013abe33 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -9532,7 +9532,7 @@ 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; > > > > @@ -9720,6 +9720,17 @@ 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; > > + } > > + break;
Shrikanth and Peter,
Sorry, I acked Shrikanth's fixup patch too quickly without seeing that Shrikanth added a "break" in the patch above. My original code did not have that break statement as I did intend the code to fall through to the "group_fully_busy" code path when there are no idle cpus in both groups. To make the compiler happy and putting in the correct logic, I refresh the patch as below.
Thanks.
Tim
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; -- 2.32.0
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