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Message-ID: <5100DC1A.9070906@linux.vnet.ibm.com>
Date: Thu, 24 Jan 2013 15:00:42 +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 01/24/2013 02:01 PM, Michael Wang wrote:
> 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.
I still can't reproduce the issue, but there are some difference
according to my default sd topology:
WYT: sbm of cpu 0
WYT: exec map
WYT: sd f051be80, idx 0, level 0, weight 4
WYT: sd f08b3700, idx 1, level 1, weight 32
WYT: sd f08b3700, idx 2, level 1, weight 32
WYT: fork map
WYT: sd f051be80, idx 0, level 0, weight 4
WYT: sd f08b3700, idx 1, level 1, weight 32
WYT: sd f08b3700, idx 2, level 1, weight 32
WYT: wake map
WYT: sd f051be80, idx 0, level 0, weight 4
WYT: sd f08b3700, idx 1, level 1, weight 32
WYT: sd f08b6300, idx 2, level 2, weight 64
WYT: affine map
WYT: affine with cpu 0 in sd f051be80, weight 4
WYT: affine with cpu 1 in sd f051be80, weight 4
WYT: affine with cpu 2 in sd f051be80, weight 4
WYT: affine with cpu 3 in sd f051be80, weight 4
...
And there are only sibling, cpu and numa level, no mc level while your
box have, but that looks harmless to me... isn't it?
This is the aim 7 results of the patched kernel, it's just fine.
Tasks jobs/min jti jobs/min/task real cpu
1 424.07 100 424.0728 14.29 4.29 Thu Jan 24
01:52:22 2013
5 2561.28 99 512.2570 11.83 8.82 Thu Jan 24
01:52:35 2013
10 5033.22 97 503.3223 12.04 16.35 Thu Jan 24
01:52:47 2013
20 10350.13 98 517.5064 11.71 28.54 Thu Jan 24
01:52:59 2013
40 20116.18 98 502.9046 12.05 62.06 Thu Jan 24
01:53:11 2013
80 39255.06 98 490.6883 12.35 122.18 Thu Jan 24
01:53:24 2013
160 69405.87 97 433.7867 13.97 234.41 Thu Jan 24
01:53:38 2013
320 111192.66 92 347.4771 17.44 463.18 Thu Jan 24
01:53:56 2013
640 158044.01 86 246.9438 24.54 920.38 Thu Jan 24
01:54:20 2013
1280 199763.07 87 156.0649 38.83 1833.75 Thu Jan 24
01:54:59 2013
2560 229933.30 81 89.8177 67.47 3665.30 Thu Jan 24
01:56:07 2013
And this is my cpu info:
processor : 63
cpu : POWER7 (raw), altivec supported
clock : 8.388608MHz
revision : 2.3 (pvr 003f 0203)
Regards,
Michael Wang
>
>> --- 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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>
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