v2:
- Rebase on top of tag sched-core-2023-08-28, also applies cleanly on
top of v6.6-rc1;
- Explain why ratelimit to once per ms in the changelog as suggested by
David Vernet;
- Collected reviewed-by and tested-by tags, thank you all for your review
and test!
After rebase, I did a new run of postgres_sysbench workload on Intel
Sapphire Rapids and the data is about the same as v1. Consider that
there is no much change in load tracking from v6.6, I've kept the old
data.
RFC v2 -> v1:
- drop RFC;
- move cfs_rq->last_update_tg_load_avg before cfs_rq->tg_load_avg_contrib;
- add Vincent's reviewed-by tag.
RFC v2:
Nitin Tekchandani noticed some scheduler functions have high cost
according to perf/cycles while running postgres_sysbench workload.
I perf/annotated the high cost functions: update_cfs_group() and
update_load_avg() and found the costs were ~90% due to accessing to
tg->load_avg. This series is an attempt to reduce the overhead of
the two functions.
Thanks to Vincent's suggestion from v1, this revision used a simpler way
to solve the overhead problem by limiting updates to tg->load_avg to at
most once per ms. Benchmark shows that it has good results and with the
rate limit in place, other optimizations in v1 don't improve performance
further so they are dropped from this revision.
Aaron Lu (1):
sched/fair: ratelimit update to tg->load_avg
kernel/sched/fair.c | 13 ++++++++++++-
kernel/sched/sched.h | 1 +
2 files changed, 13 insertions(+), 1 deletion(-)
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2.41.0