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From: Parth Shah <parth@linux.ibm.com>
To: subhra mazumdar <subhra.mazumdar@oracle.com>,
	linux-kernel@vger.kernel.org
Cc: peterz@infradead.org, mingo@redhat.com, tglx@linutronix.de,
	steven.sistare@oracle.com, dhaval.giani@oracle.com,
	daniel.lezcano@linaro.org, vincent.guittot@linaro.org,
	viresh.kumar@linaro.org, tim.c.chen@linux.intel.com,
	mgorman@techsingularity.net, patrick.bellasi@arm.com
Subject: Re: [RFC PATCH 0/9] Task latency-nice
Date: Thu, 5 Sep 2019 11:25:38 +0530	[thread overview]
Message-ID: <cef0717a-e1da-c4a3-9fd0-ddb0914e3850@linux.ibm.com> (raw)
In-Reply-To: <20190830174944.21741-1-subhra.mazumdar@oracle.com>

Hi Subhra,

On 8/30/19 11:19 PM, subhra mazumdar wrote:
> Introduce new per task property latency-nice for controlling scalability
> in scheduler idle CPU search path. Valid latency-nice values are from 1 to
> 100 indicating 1% to 100% search of the LLC domain in select_idle_cpu. New
> CPU cgroup file cpu.latency-nice is added as an interface to set and get.
> All tasks in the same cgroup share the same latency-nice value. Using a
> lower latency-nice value can help latency intolerant tasks e.g very short
> running OLTP threads where full LLC search cost can be significant compared
> to run time of the threads. The default latency-nice value is 5.
> 
> In addition to latency-nice, it also adds a new sched feature SIS_CORE to
> be able to disable idle core search altogether which is costly and hurts
> more than it helps in short running workloads.
> 
> Finally it also introduces a new per-cpu variable next_cpu to track
> the limit of search so that every time search starts from where it ended.
> This rotating search window over cpus in LLC domain ensures that idle
> cpus are eventually found in case of high load.
> 
> Uperf pingpong on 2 socket, 44 core and 88 threads Intel x86 machine with
> message size = 8k (higher is better):
> threads baseline   latency-nice=5,SIS_CORE     latency-nice=5,NO_SIS_CORE 
> 8       64.66      64.38 (-0.43%)              64.79 (0.2%)
> 16      123.34     122.88 (-0.37%)             125.87 (2.05%)
> 32      215.18     215.55 (0.17%)              247.77 (15.15%)
> 48      278.56     321.6 (15.45%)              321.2 (15.3%)
> 64      259.99     319.45 (22.87%)             333.95 (28.44%)
> 128     431.1      437.69 (1.53%)              431.09 (0%)
> 

The result seems to be appealing with your experimental setup.
BTW, do you have any plans of load balancing as well based on latency niceness
of the tasks? It seems to be a more interesting case when we give pack the lower
latency sensitive tasks on fewer CPUs.

Also, do you see any workload results showing performance regression with NO_SIS_CORE?


Thanks,
Parth


  parent reply	other threads:[~2019-09-05  5:55 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-30 17:49 [RFC PATCH 0/9] Task latency-nice subhra mazumdar
2019-08-30 17:49 ` [RFC PATCH 1/9] sched,cgroup: Add interface for latency-nice subhra mazumdar
2019-09-04 17:32   ` Tim Chen
2019-09-05  6:15     ` Parth Shah
2019-09-05 10:11       ` Patrick Bellasi
2019-09-06 12:22         ` Parth Shah
2019-09-05  8:31   ` Peter Zijlstra
2019-09-05  9:45     ` Patrick Bellasi
2019-09-05 10:46       ` Peter Zijlstra
2019-09-05 11:13         ` Qais Yousef
2019-09-05 11:30           ` Peter Zijlstra
2019-09-05 11:40             ` Patrick Bellasi
2019-09-05 11:48               ` Peter Zijlstra
2019-09-05 13:32                 ` Qais Yousef
2019-09-05 11:47             ` Qais Yousef
2020-04-16  0:02               ` Joel Fernandes
2020-04-16 17:23                 ` Dietmar Eggemann
2020-04-18 16:01                   ` Joel Fernandes
2020-04-20 11:26                     ` Parth Shah
2020-04-20 19:14                       ` Joel Fernandes
2020-04-20 11:47                     ` Qais Yousef
2020-04-20 19:10                       ` Joel Fernandes
2019-09-05 11:30           ` Patrick Bellasi
2019-09-05 11:47             ` Peter Zijlstra
2019-09-05 11:18         ` Patrick Bellasi
2019-09-05 11:40           ` Peter Zijlstra
2019-09-05 11:46             ` Patrick Bellasi
2019-09-05 11:46           ` Valentin Schneider
2019-09-05 13:07             ` Patrick Bellasi
2019-09-05 14:48               ` Valentin Schneider
2019-09-06 12:45               ` Parth Shah
2019-09-06 14:13                 ` Valentin Schneider
2019-09-06 14:32                   ` Vincent Guittot
2019-09-06 17:10                   ` Parth Shah
2019-09-06 22:50                     ` Valentin Schneider
2019-09-06 12:31       ` Parth Shah
2019-09-05 10:05   ` Patrick Bellasi
2019-09-05 10:48     ` Peter Zijlstra
2019-08-30 17:49 ` [RFC PATCH 2/9] sched: add search limit as per latency-nice subhra mazumdar
2019-09-05  6:22   ` Parth Shah
2019-08-30 17:49 ` [RFC PATCH 3/9] sched: add sched feature to disable idle core search subhra mazumdar
2019-09-05 10:17   ` Patrick Bellasi
2019-09-05 22:02     ` Subhra Mazumdar
2019-08-30 17:49 ` [RFC PATCH 4/9] sched: SIS_CORE " subhra mazumdar
2019-09-05 10:19   ` Patrick Bellasi
2019-08-30 17:49 ` [RFC PATCH 5/9] sched: Define macro for number of CPUs in core subhra mazumdar
2019-08-30 17:49 ` [RFC PATCH 6/9] x86/smpboot: Optimize cpumask_weight_sibling macro for x86 subhra mazumdar
2019-08-30 17:49 ` [RFC PATCH 7/9] sched: search SMT before LLC domain subhra mazumdar
2019-09-05  9:31   ` Peter Zijlstra
2019-09-05 20:40     ` Subhra Mazumdar
2019-08-30 17:49 ` [RFC PATCH 8/9] sched: introduce per-cpu var next_cpu to track search limit subhra mazumdar
2019-08-30 17:49 ` [RFC PATCH 9/9] sched: rotate the cpu search window for better spread subhra mazumdar
2019-09-05  6:37   ` Parth Shah
2019-09-05  5:55 ` Parth Shah [this message]
2019-09-05 10:31 ` [RFC PATCH 0/9] Task latency-nice Patrick Bellasi

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