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Message-ID: <5100CE1F.7080704@linux.vnet.ibm.com>
Date: Thu, 24 Jan 2013 14:01:03 +0800
From: Michael Wang <wangyun@...ux.vnet.ibm.com>
To: Mike Galbraith <bitbucket@...ine.de>
CC: linux-kernel@...r.kernel.org, mingo@...hat.com,
peterz@...radead.org, mingo@...nel.org, a.p.zijlstra@...llo.nl
Subject: Re: [RFC PATCH 0/2] sched: simplify the select_task_rq_fair()
On 01/23/2013 05:32 PM, Mike Galbraith wrote:
[snip]
> ---
> include/linux/topology.h | 6 ++---
> kernel/sched/core.c | 41 ++++++++++++++++++++++++++++++-------
> kernel/sched/fair.c | 52 +++++++++++++++++++++++++++++------------------
> 3 files changed, 70 insertions(+), 29 deletions(-)
>
> --- a/include/linux/topology.h
> +++ b/include/linux/topology.h
> @@ -95,7 +95,7 @@ int arch_update_cpu_topology(void);
> | 1*SD_BALANCE_NEWIDLE \
> | 1*SD_BALANCE_EXEC \
> | 1*SD_BALANCE_FORK \
> - | 0*SD_BALANCE_WAKE \
> + | 1*SD_BALANCE_WAKE \
> | 1*SD_WAKE_AFFINE \
> | 1*SD_SHARE_CPUPOWER \
> | 1*SD_SHARE_PKG_RESOURCES \
> @@ -126,7 +126,7 @@ int arch_update_cpu_topology(void);
> | 1*SD_BALANCE_NEWIDLE \
> | 1*SD_BALANCE_EXEC \
> | 1*SD_BALANCE_FORK \
> - | 0*SD_BALANCE_WAKE \
> + | 1*SD_BALANCE_WAKE \
> | 1*SD_WAKE_AFFINE \
> | 0*SD_SHARE_CPUPOWER \
> | 1*SD_SHARE_PKG_RESOURCES \
> @@ -156,7 +156,7 @@ int arch_update_cpu_topology(void);
> | 1*SD_BALANCE_NEWIDLE \
> | 1*SD_BALANCE_EXEC \
> | 1*SD_BALANCE_FORK \
> - | 0*SD_BALANCE_WAKE \
> + | 1*SD_BALANCE_WAKE \
> | 1*SD_WAKE_AFFINE \
> | 0*SD_SHARE_CPUPOWER \
> | 0*SD_SHARE_PKG_RESOURCES \
I've enabled WAKE flag on my box like you did, but still can't see
regression, and I've just tested on a power server with 64 cpu, also
failed to reproduce the issue (not compared with virgin yet, but can't
see collapse).
I will do more testing on the power box to confirm it.
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5609,11 +5609,39 @@ static void update_top_cache_domain(int
> static int sbm_max_level;
> DEFINE_PER_CPU_SHARED_ALIGNED(struct sched_balance_map, sbm_array);
>
> +static void debug_sched_balance_map(int cpu)
> +{
> + int i, type, level = 0;
> + struct sched_balance_map *sbm = &per_cpu(sbm_array, cpu);
> +
> + printk("WYT: sbm of cpu %d\n", cpu);
> +
> + for (type = 0; type < SBM_MAX_TYPE; type++) {
> + if (type == SBM_EXEC_TYPE)
> + printk("WYT: \t exec map\n");
> + else if (type == SBM_FORK_TYPE)
> + printk("WYT: \t fork map\n");
> + else if (type == SBM_WAKE_TYPE)
> + printk("WYT: \t wake map\n");
> +
> + for (level = 0; level < sbm_max_level; level++) {
> + if (sbm->sd[type][level])
> + printk("WYT: \t\t sd %x, idx %d, level %d, weight %d\n", sbm->sd[type][level], level, sbm->sd[type][level]->level, sbm->sd[type][level]->span_weight);
> + }
> + }
> +
> + printk("WYT: \t affine map\n");
> +
> + for_each_possible_cpu(i) {
> + if (sbm->affine_map[i])
> + printk("WYT: \t\t affine with cpu %x in sd %x, weight %d\n", i, sbm->affine_map[i], sbm->affine_map[i]->span_weight);
> + }
> +}
> +
> static void build_sched_balance_map(int cpu)
> {
> struct sched_balance_map *sbm = &per_cpu(sbm_array, cpu);
> struct sched_domain *sd = cpu_rq(cpu)->sd;
> - struct sched_domain *top_sd = NULL;
> int i, type, level = 0;
>
> memset(sbm->top_level, 0, sizeof((*sbm).top_level));
> @@ -5656,11 +5684,9 @@ static void build_sched_balance_map(int
> * fill the hole to get lower level sd easily.
> */
> for (type = 0; type < SBM_MAX_TYPE; type++) {
> - level = sbm->top_level[type];
> - top_sd = sbm->sd[type][level];
> - if ((++level != sbm_max_level) && top_sd) {
> - for (; level < sbm_max_level; level++)
> - sbm->sd[type][level] = top_sd;
> + for (level = 1; level < sbm_max_level; level++) {
> + if (!sbm->sd[type][level])
> + sbm->sd[type][level] = sbm->sd[type][level - 1];
> }
> }
> }
> @@ -5719,6 +5745,7 @@ cpu_attach_domain(struct sched_domain *s
> * destroy_sched_domains() already do the work.
> */
> build_sched_balance_map(cpu);
> +//MIKE debug_sched_balance_map(cpu);
> rcu_assign_pointer(rq->sbm, sbm);
> }
>
> @@ -6220,7 +6247,7 @@ sd_numa_init(struct sched_domain_topolog
> | 1*SD_BALANCE_NEWIDLE
> | 0*SD_BALANCE_EXEC
> | 0*SD_BALANCE_FORK
> - | 0*SD_BALANCE_WAKE
> + | 1*SD_BALANCE_WAKE
> | 0*SD_WAKE_AFFINE
> | 0*SD_SHARE_CPUPOWER
> | 0*SD_SHARE_PKG_RESOURCES
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3312,7 +3312,7 @@ static int select_idle_sibling(struct ta
> static int
> select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
> {
> - struct sched_domain *sd = NULL;
> + struct sched_domain *sd = NULL, *tmp;
> int cpu = smp_processor_id();
> int prev_cpu = task_cpu(p);
> int new_cpu = cpu;
> @@ -3376,31 +3376,45 @@ select_task_rq_fair(struct task_struct *
>
> balance_path:
> new_cpu = (sd_flag & SD_BALANCE_WAKE) ? prev_cpu : cpu;
> - sd = sbm->sd[type][sbm->top_level[type]];
> + sd = tmp = sbm->sd[type][sbm->top_level[type]];
>
> while (sd) {
> int load_idx = sd->forkexec_idx;
> - struct sched_group *sg = NULL;
> + struct sched_group *group;
> + int weight;
> +
> + if (!(sd->flags & sd_flag)) {
> + sd = sd->child;
> + continue;
> + }
>
> if (sd_flag & SD_BALANCE_WAKE)
> load_idx = sd->wake_idx;
>
> - sg = find_idlest_group(sd, p, cpu, load_idx);
> - if (!sg)
> - goto next_sd;
> -
> - new_cpu = find_idlest_cpu(sg, p, cpu);
> - if (new_cpu != -1)
> - cpu = new_cpu;
> -next_sd:
> - if (!sd->level)
> - break;
> -
> - sbm = cpu_rq(cpu)->sbm;
> - if (!sbm)
> - break;
> -
> - sd = sbm->sd[type][sd->level - 1];
May be we could test part by part? I'm planing to write another debug
patch, by which we could compare just part of the two ways, will send to
you when I finished it.
Regards,
Michael Wang
> + group = find_idlest_group(sd, p, cpu, load_idx);
> + if (!group) {
> + sd = sd->child;
> + continue;
> + }
> +
> + new_cpu = find_idlest_cpu(group, p, cpu);
> + if (new_cpu == -1 || new_cpu == cpu) {
> + /* Now try balancing at a lower domain level of cpu */
> + sd = sd->child;
> + continue;
> + }
> +
> + /* Now try balancing at a lower domain level of new_cpu */
> + cpu = new_cpu;
> + weight = sd->span_weight;
> + sd = NULL;
> + for_each_domain(cpu, tmp) {
> + if (weight <= tmp->span_weight)
> + break;
> + if (tmp->flags & sd_flag)
> + sd = tmp;
> + }
> + /* while loop will break here if sd == NULL */
> }
>
> unlock:
>
>
> --
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