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From: subhra mazumdar <subhra.mazumdar@oracle.com>
To: 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, parth@linux.ibm.com,
	patrick.bellasi@arm.com
Subject: [RFC PATCH 0/9] Task latency-nice
Date: Fri, 30 Aug 2019 10:49:35 -0700
Message-ID: <20190830174944.21741-1-subhra.mazumdar@oracle.com> (raw)

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%)

subhra mazumdar (9):
  sched,cgroup: Add interface for latency-nice
  sched: add search limit as per latency-nice
  sched: add sched feature to disable idle core search
  sched: SIS_CORE to disable idle core search
  sched: Define macro for number of CPUs in core
  x86/smpboot: Optimize cpumask_weight_sibling macro for x86
  sched: search SMT before LLC domain
  sched: introduce per-cpu var next_cpu to track search limit
  sched: rotate the cpu search window for better spread

 arch/x86/include/asm/smp.h      |  1 +
 arch/x86/include/asm/topology.h |  1 +
 arch/x86/kernel/smpboot.c       | 17 ++++++++++++++++-
 include/linux/sched.h           |  1 +
 include/linux/topology.h        |  4 ++++
 kernel/sched/core.c             | 42 +++++++++++++++++++++++++++++++++++++++++
 kernel/sched/fair.c             | 34 +++++++++++++++++++++------------
 kernel/sched/features.h         |  1 +
 kernel/sched/sched.h            |  9 +++++++++
 9 files changed, 97 insertions(+), 13 deletions(-)

-- 
2.9.3


             reply index

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-30 17:49 subhra mazumdar [this message]
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 ` [RFC PATCH 0/9] Task latency-nice Parth Shah
2019-09-05 10:31 ` Patrick Bellasi

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