Re: High SYS CPU - need advise

Merlin Moncure escribió:

> ok, excellent. reviewing the log, this immediately caught my eye:
>
> recvfrom(8, "\27\3\1\0@", 5, 0, NULL, NULL) = 5
> recvfrom(8, "\327\327\nl\231LD\211\346\243(at)WW\254\244\363C\326\247\341\177\255\263~\327HDv-\3466\353"...,
> 64, 0, NULL, NULL) = 64
> select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 2000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 3000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 4000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 6000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 7000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 8000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 9000}) = 0 (Timeout)
> semop(41713721, {{2, 1, 0}}, 1) = 0
> lseek(295, 0, SEEK_END) = 0
> lseek(296, 0, SEEK_END) = 8192
>
> this is definitely pointing to spinlock issue.

I met Rik van Riel (Linux kernel hacker) recently and we chatted about
this briefly. He strongly suggested that we should consider using
futexes on Linux instead of spinlocks; the big advantage being that
futexes sleep instead of spinning when contention is high. That would
reduce the system load in this scenario.

--
Álvaro Herrera http://www.2ndQuadrant.com/
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