4 ms·
After the latency spike does the smaps output still list the same amount of AnonHugePages?
by nteon 12y ago
After the latency spike does the smaps output still list the same amount of AnonHugePages?
- antirez 12y agoCan't test it right now, but seems smart, to check if they got split into smaller pages.
- nteon 12y agoI just tested - while running the redis-benchmark command you listed after a BGSAVE smaps lists all anonymous memory as AnonHugePages. So it ends up as THP, although I suppose its possible that it is broken into 4k pages and then adjacent 4k pages are merged back into huge pages. Will see if I can figure out how the lazy PTE copying works.
- nteon 12y agoas 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 https://www.kernel.org/doc/Documentation/vm/ksm.txt
- antirez 12y agoStrange... you should definitely see it if you are using jemalloc now that it's clear it's about mass-COW.