Messages in this thread | | | From | subhra mazumdar <> | Subject | [RFC PATCH 0/9] Task latency-nice | Date | Fri, 30 Aug 2019 10:49:35 -0700 |
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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
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