Comment on Redis latency spikes and the Linux kernel: a few more detailsparentComments−nteon11yas a followup, I don't see large latency with huge pages, but I have kernel samepage merging disabled.I would be interested if this also decreases latency for you:echo 2 > /sys/kernel/mm/ksm/runAlso check stats here: /sys/kernel/mm/ksm/*And some documentation here: https://www.kernel.org/doc/Documentation/vm/ksm.txt−antirez11yStrange... you should definitely see it if you are using jemalloc now that it's clear it's about mass-COW.−nteon11yI do see it now... wasn't testing right before. Goes away as you say when disabling transparent THP. KSM has no effect, contrary to what I thought earlier.−antirez11yThanks a lot for independent confirmation of the issue.
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as a followup, I don't see large latency with huge pages, but I have kernel samepage merging disabled.
I would be interested if this also decreases latency for you:
echo 2 > /sys/kernel/mm/ksm/run
Also check stats here: /sys/kernel/mm/ksm/*
And some documentation here: https://www.kernel.org/doc/Documentation/vm/ksm.txt
Strange... you should definitely see it if you are using jemalloc now that it's clear it's about mass-COW.
I do see it now... wasn't testing right before. Goes away as you say when disabling transparent THP. KSM has no effect, contrary to what I thought earlier.
Thanks a lot for independent confirmation of the issue.