Linaro-open-discussions November 2021

linaro-open-discussions@op-lists.linaro.org

10 participants
13 discussions

by Jammy Zhou

Hi all, The monthly meeting will happen next Monday (Oct 25th), please let me know if you have any topics to cover. Thanks, Jammy

2 years, 5 months

[PATCH 0/2] Wake task within the same cluster of waker if possible

by Yicong Yang

This is the follow-up work to support cluster scheduler. Previously we have added cluster level in the scheduler[1] to make tasks spread between clusters to bring more memory bandwidth and decrease cache contention. But it may hurt some workloads which are sensitive to the communication latency as they will be placed across clusters. We modified the select_idle_cpu() on the wake affine path in this series, expecting the wake affined task to be woken more likely on the same cluster with the waker. The latency will be decreased as the waker and wakee in the same cluster may benefit from the hot L3 cache tag. [1] https://lore.kernel.org/lkml/20210924085104.44806-1-21cnbao@gmail.com/ Hi Tim and Barry, This the modified patch of packing path of cluster scheduler and tests have been done on Kunpeng 920 2-socket 4-NUMA 128core platform, with 8 clusters on each NUMA. Patches based on 5.15-rc1. Barry Song (2): sched: Add per_cpu cluster domain info sched/fair: Scan from the first cpu of cluster if presents in select_idle_cpu include/linux/sched/sd_flags.h | 9 +++++++++ include/linux/sched/topology.h | 2 +- kernel/sched/fair.c | 10 +++++++--- kernel/sched/sched.h | 1 + kernel/sched/topology.c | 5 +++++ 5 files changed, 23 insertions(+), 4 deletions(-) -- 2.33.0

2 years, 5 months

SCMI protocol for interconnect scaling

by Georgi Djakov

Hi all, I am recently getting questions about hooking the interconnect framework to SCMI, so i am starting a discussion on this problem and see who might be interested in it. The SCMI spec contains various protocols like the "Performance domain management protocol". But none of the protocols mentioned in the current spec (3.0) seem to fit well into the concept we are using to scale interconnect bandwidth in Linux. I see that people are working in this area and there is already some support for clocks, resets etc. I am wondering what would be the right approach to support also interconnect bus scaling via SCMI. The interconnect framework is part of the linux kernel and it's goal is to manage the hardware and tune it to the most optimal power- performance profile according to the aggregated bandwidth demand between the various endpoints in the system (SoC). This is based on the requests coming from consumer drivers. As interconnects scaling does not map directly to any of the currently available protocols in the SCMI spec, i am curious whether there is work in progress on some other protocol that could support managing resources based on path endpoints (instead of a single ID). The interconnect framework doesn't populate every possible path, but it exposes endpoints to client drivers and the path lookup is dynamic, based on what the clients request. Maybe the SCMI host could also expose all possible endpoints and let the guest request a path from the host, based on those endpoints. There are already suggestions to create vendor-specific SCMI protocols for that, but i fear that we may end up with more than one protocol for the same thing, so that's why it might be best to discuss it in public and have a common solution that works for everyone. Thanks, Georgi

2 years, 5 months

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Linaro-open-discussions November 2021