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From:Dan Nelson Date:April 12 2001 3:23am
Subject:Re: mysql uses 99% cpu under freebsd 4.3
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In the last episode (Apr 11), Ken Menzel said:
> The list reject my trace (it was too large),  so here is a smaller
> one!  Stops after info from first top starts showing CPU usage of 99%
> Ken
> Hi Tim,  I just had it happen.  Overall average 14 queries per second
> on this machine.  Single CPU Kernel Dell 2400 600MHZ FreeBSD-stable
> from January.  Almost generic kernel.  I have attahced some output
> from truss, followed by 'top' followed by the stop and start of
> mysql, followed by the output from 'top' again.  Hope this helps
> someone!
> lseek(229,0x3c378,0)                             = 246648 (0x3c378)
> read(0xe5,0xbf39ef98,0x14)                       = 20 (0x14)
> pread(0xe5,0x1843a018,0x9f,0x0,0x3c385,0x0)      = 159 (0x9f)
> lseek(229,0x41d84,0)                             = 269700 (0x41d84)
> read(0xe5,0xbf39ef98,0x14)                       = 20 (0x14)
> pread(0xe5,0x1843a0b7,0x10,0x0,0x41d88,0x0)      = 16 (0x10)

This looks like a perfectly normal mysql truss.  Lots of disk I/O, and
it looks like you're got a pretty small record length (20-byte reads?
although the combo of lseek+read and pread on the same datafile is
puzzling.  Maybe it's a table with a couple of INT/CHAR columns and a
BLOB column?).

Does a "show processlist" say there's a query running?   An interesting
thing to see might be the output of a couple seconds of "iostat 1" and
"vmstat 1", to see how much disk and syscall activity there is.

	Dan Nelson
mysql uses 99% cpu under freebsd 4.3Ken Menzel11 Apr
  • Re: mysql uses 99% cpu under freebsd 4.3Tim Bunce12 Apr
  • Re: mysql uses 99% cpu under freebsd 4.3Dan Nelson12 Apr
  • Re: mysql uses 99% cpu under freebsd 4.3Ken Menzel12 Apr
    • Re: mysql uses 99% cpu under freebsd 4.3Mark Worsdall12 Apr