From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Valentin Schneider <valentin.schneider@arm.com>,
Aubrey Li <aubrey.li@linux.intel.com>,
Barry Song <song.bao.hua@hisilicon.com>,
Mike Galbraith <efault@gmx.de>,
Gautham Shenoy <gautham.shenoy@amd.com>,
K Prateek Nayak <kprateek.nayak@amd.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] sched/fair: Improve consistency of allowed NUMA balance calculations
Date: Mon, 14 Feb 2022 15:56:42 +0530 [thread overview]
Message-ID: <20220214102642.GH618915@linux.vnet.ibm.com> (raw)
In-Reply-To: <20220208094334.16379-2-mgorman@techsingularity.net>
* Mel Gorman <mgorman@techsingularity.net> [2022-02-08 09:43:33]:
> There are inconsistencies when determining if a NUMA imbalance is allowed
> that should be corrected.
>
> o allow_numa_imbalance changes types and is not always examining
> the destination group so both the type should be corrected as
> well as the naming.
> o find_idlest_group uses the sched_domain's weight instead of the
> group weight which is different to find_busiest_group
> o find_busiest_group uses the source group instead of the destination
> which is different to task_numa_find_cpu
> o Both find_idlest_group and find_busiest_group should account
> for the number of running tasks if a move was allowed to be
> consistent with task_numa_find_cpu
>
> Fixes: 7d2b5dd0bcc4 ("sched/numa: Allow a floating imbalance between NUMA nodes")
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> ---
> kernel/sched/fair.c | 18 ++++++++++--------
> 1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 095b0aa378df..4592ccf82c34 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -9003,9 +9003,10 @@ static bool update_pick_idlest(struct sched_group *idlest,
> * This is an approximation as the number of running tasks may not be
> * related to the number of busy CPUs due to sched_setaffinity.
> */
> -static inline bool allow_numa_imbalance(int dst_running, int dst_weight)
> +static inline bool
> +allow_numa_imbalance(unsigned int running, unsigned int weight)
> {
> - return (dst_running < (dst_weight >> 2));
> + return (running < (weight >> 2));
> }
>
> /*
> @@ -9139,12 +9140,13 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
> return idlest;
> #endif
> /*
> - * Otherwise, keep the task on this node to stay close
> - * its wakeup source and improve locality. If there is
> - * a real need of migration, periodic load balance will
> - * take care of it.
> + * Otherwise, keep the task close to the wakeup source
> + * and improve locality if the number of running tasks
> + * would remain below threshold where an imbalance is
> + * allowed. If there is a real need of migration,
> + * periodic load balance will take care of it.
> */
> - if (allow_numa_imbalance(local_sgs.sum_nr_running, sd->span_weight))
> + if (allow_numa_imbalance(local_sgs.sum_nr_running + 1, local_sgs.group_weight))
> return NULL;
> }
>
> @@ -9350,7 +9352,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
> /* Consider allowing a small imbalance between NUMA groups */
> if (env->sd->flags & SD_NUMA) {
> env->imbalance = adjust_numa_imbalance(env->imbalance,
> - busiest->sum_nr_running, busiest->group_weight);
> + local->sum_nr_running + 1, local->group_weight);
> }
>
> return;
> --
> 2.31.1
>
Looks good to me.
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
--
Thanks and Regards
Srikar Dronamraju
next prev parent reply other threads:[~2022-02-14 11:00 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-08 9:43 [PATCH v6 0/2] Adjust NUMA imbalance for multiple LLCs Mel Gorman
2022-02-08 9:43 ` [PATCH 1/2] sched/fair: Improve consistency of allowed NUMA balance calculations Mel Gorman
2022-02-08 15:06 ` Gautham R. Shenoy
2022-02-14 9:48 ` Vincent Guittot
2022-02-14 10:26 ` Srikar Dronamraju [this message]
2022-02-14 10:30 ` [tip: sched/core] " tip-bot2 for Mel Gorman
2022-02-08 9:43 ` [PATCH 2/2] sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs Mel Gorman
2022-02-08 16:19 ` Gautham R. Shenoy
2022-02-09 5:10 ` K Prateek Nayak
2022-02-09 10:33 ` Mel Gorman
2022-02-11 19:02 ` Jirka Hladky
2022-02-14 10:27 ` Srikar Dronamraju
2022-02-14 10:30 ` [tip: sched/core] " tip-bot2 for Mel Gorman
2022-02-14 11:03 ` [PATCH 2/2] " Vincent Guittot
2022-02-09 9:38 ` [PATCH v6 0/2] Adjust NUMA imbalance for " Peter Zijlstra
-- strict thread matches above, loose matches on Subject: below --
2022-02-03 14:46 [PATCH v5 " Mel Gorman
2022-02-03 14:46 ` [PATCH 1/2] sched/fair: Improve consistency of allowed NUMA balance calculations Mel Gorman
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