| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Wed, 10 Jul 2013 09:52:09 +0800
From: Sam Ben <sam.bennn@...il.com>
To: Michael Wang <wangyun@...ux.vnet.ibm.com>
CC: LKML <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Mike Galbraith <efault@....de>, Alex Shi <alex.shi@...el.com>,
Namhyung Kim <namhyung@...nel.org>,
Paul Turner <pjt@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>,
Ram Pai <linuxram@...ibm.com>
Subject: Re: [PATCH v3 1/2] sched: smart wake-affine foundation
On 07/08/2013 10:36 AM, Michael Wang wrote:
> Hi, Sam
>
> On 07/07/2013 09:31 AM, Sam Ben wrote:
>> On 07/04/2013 12:55 PM, Michael Wang wrote:
>>> wake-affine stuff is always trying to pull wakee close to waker, by
>>> theory,
>>> this will bring benefit if waker's cpu cached hot data for wakee, or the
>>> extreme ping-pong case.
>> What's the meaning of ping-pong case?
> PeterZ explained it well in here:
>
> https://lkml.org/lkml/2013/3/7/332
>
> And you could try to compare:
> taskset 1 perf bench sched pipe
> with
> perf bench sched pipe
Why sched pipe is special?
>
> to confirm it ;-)
>
> Regards,
> Michael Wang
>
>>> And testing show it could benefit hackbench 15% at most.
>>>
>>> However, the whole stuff is somewhat blindly and time-consuming, some
>>> workload therefore suffer.
>>>
>>> And testing show it could damage pgbench 50% at most.
>>>
>>> Thus, wake-affine stuff should be more smart, and realise when to stop
>>> it's thankless effort.
>>>
>>> This patch introduced 'nr_wakee_switch', which will be increased each
>>> time the task switch it's wakee.
>>>
>>> So a high 'nr_wakee_switch' means the task has more than one wakee, and
>>> bigger the number, higher the wakeup frequency.
>>>
>>> Now when making the decision on whether to pull or not, pay attention on
>>> the wakee with a high 'nr_wakee_switch', pull such task may benefit
>>> wakee,
>>> but also imply that waker will face cruel competition later, it could be
>>> very cruel or very fast depends on the story behind 'nr_wakee_switch',
>>> whatever, waker therefore suffer.
>>>
>>> Furthermore, if waker also has a high 'nr_wakee_switch', imply that
>>> multiple
>>> tasks rely on it, then waker's higher latency will damage all of them,
>>> pull
>>> wakee seems to be a bad deal.
>>>
>>> Thus, when 'waker->nr_wakee_switch / wakee->nr_wakee_switch' become
>>> higher
>>> and higher, the deal seems to be worse and worse.
>>>
>>> The patch therefore help wake-affine stuff to stop it's work when:
>>>
>>> wakee->nr_wakee_switch > factor &&
>>> waker->nr_wakee_switch > (factor * wakee->nr_wakee_switch)
>>>
>>> The factor here is the node-size of current-cpu, so bigger node will lead
>>> to more pull since the trial become more severe.
>>>
>>> After applied the patch, pgbench show 40% improvement at most.
>>>
>>> Test:
>>> Tested with 12 cpu X86 server and tip 3.10.0-rc7.
>>>
>>> pgbench base smart
>>>
>>> | db_size | clients | tps | | tps |
>>> +---------+---------+-------+ +-------+
>>> | 22 MB | 1 | 10598 | | 10796 |
>>> | 22 MB | 2 | 21257 | | 21336 |
>>> | 22 MB | 4 | 41386 | | 41622 |
>>> | 22 MB | 8 | 51253 | | 57932 |
>>> | 22 MB | 12 | 48570 | | 54000 |
>>> | 22 MB | 16 | 46748 | | 55982 | +19.75%
>>> | 22 MB | 24 | 44346 | | 55847 | +25.93%
>>> | 22 MB | 32 | 43460 | | 54614 | +25.66%
>>> | 7484 MB | 1 | 8951 | | 9193 |
>>> | 7484 MB | 2 | 19233 | | 19240 |
>>> | 7484 MB | 4 | 37239 | | 37302 |
>>> | 7484 MB | 8 | 46087 | | 50018 |
>>> | 7484 MB | 12 | 42054 | | 48763 |
>>> | 7484 MB | 16 | 40765 | | 51633 | +26.66%
>>> | 7484 MB | 24 | 37651 | | 52377 | +39.11%
>>> | 7484 MB | 32 | 37056 | | 51108 | +37.92%
>>> | 15 GB | 1 | 8845 | | 9104 |
>>> | 15 GB | 2 | 19094 | | 19162 |
>>> | 15 GB | 4 | 36979 | | 36983 |
>>> | 15 GB | 8 | 46087 | | 49977 |
>>> | 15 GB | 12 | 41901 | | 48591 |
>>> | 15 GB | 16 | 40147 | | 50651 | +26.16%
>>> | 15 GB | 24 | 37250 | | 52365 | +40.58%
>>> | 15 GB | 32 | 36470 | | 50015 | +37.14%
>>>
>>> CC: Ingo Molnar <mingo@...nel.org>
>>> CC: Peter Zijlstra <peterz@...radead.org>
>>> CC: Mike Galbraith <efault@....de>
>>> Signed-off-by: Michael Wang <wangyun@...ux.vnet.ibm.com>
>>> ---
>>> include/linux/sched.h | 3 +++
>>> kernel/sched/fair.c | 47
>>> +++++++++++++++++++++++++++++++++++++++++++++++
>>> 2 files changed, 50 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/include/linux/sched.h b/include/linux/sched.h
>>> index 178a8d9..1c996c7 100644
>>> --- a/include/linux/sched.h
>>> +++ b/include/linux/sched.h
>>> @@ -1041,6 +1041,9 @@ struct task_struct {
>>> #ifdef CONFIG_SMP
>>> struct llist_node wake_entry;
>>> int on_cpu;
>>> + struct task_struct *last_wakee;
>>> + unsigned long nr_wakee_switch;
>>> + unsigned long last_switch_decay;
>>> #endif
>>> int on_rq;
>>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>>> index c61a614..a4ddbf5 100644
>>> --- a/kernel/sched/fair.c
>>> +++ b/kernel/sched/fair.c
>>> @@ -2971,6 +2971,23 @@ static unsigned long cpu_avg_load_per_task(int
>>> cpu)
>>> return 0;
>>> }
>>> +static void record_wakee(struct task_struct *p)
>>> +{
>>> + /*
>>> + * Rough decay(wiping) for cost saving, don't worry
>>> + * about the boundary, really active task won't care
>>> + * the loose.
>>> + */
>>> + if (jiffies > current->last_switch_decay + HZ) {
>>> + current->nr_wakee_switch = 0;
>>> + current->last_switch_decay = jiffies;
>>> + }
>>> +
>>> + if (current->last_wakee != p) {
>>> + current->last_wakee = p;
>>> + current->nr_wakee_switch++;
>>> + }
>>> +}
>>> static void task_waking_fair(struct task_struct *p)
>>> {
>>> @@ -2991,6 +3008,7 @@ static void task_waking_fair(struct task_struct *p)
>>> #endif
>>> se->vruntime -= min_vruntime;
>>> + record_wakee(p);
>>> }
>>> #ifdef CONFIG_FAIR_GROUP_SCHED
>>> @@ -3109,6 +3127,28 @@ static inline unsigned long
>>> effective_load(struct task_group *tg, int cpu,
>>> #endif
>>> +static int wake_wide(struct task_struct *p)
>>> +{
>>> + int factor = nr_cpus_node(cpu_to_node(smp_processor_id()));
>>> +
>>> + /*
>>> + * Yeah, it's the switching-frequency, could means many wakee or
>>> + * rapidly switch, use factor here will just help to automatically
>>> + * adjust the loose-degree, so bigger node will lead to more pull.
>>> + */
>>> + if (p->nr_wakee_switch > factor) {
>>> + /*
>>> + * wakee is somewhat hot, it needs certain amount of cpu
>>> + * resource, so if waker is far more hot, prefer to leave
>>> + * it alone.
>>> + */
>>> + if (current->nr_wakee_switch > (factor * p->nr_wakee_switch))
>>> + return 1;
>>> + }
>>> +
>>> + return 0;
>>> +}
>>> +
>>> static int wake_affine(struct sched_domain *sd, struct task_struct
>>> *p, int sync)
>>> {
>>> s64 this_load, load;
>>> @@ -3118,6 +3158,13 @@ static int wake_affine(struct sched_domain *sd,
>>> struct task_struct *p, int sync)
>>> unsigned long weight;
>>> int balanced;
>>> + /*
>>> + * If we wake multiple tasks be careful to not bounce
>>> + * ourselves around too much.
>>> + */
>>> + if (wake_wide(p))
>>> + return 0;
>>> +
>>> idx = sd->wake_idx;
>>> this_cpu = smp_processor_id();
>>> prev_cpu = task_cpu(p);
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>> the body of a message to majordomo@...r.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at http://www.tux.org/lkml/
>>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists