On 04/21/2017 04:38 AM, Mark Geisert wrote:
I can reproduce your issue on a real Win7.64 machine so that removes
any possible virtual machine root cause. I was running 'top -s1' in
one window while running your testcase in another window. Yes, top
froze for many seconds at a time, then caught its display up, only to
freeze again repeatedly. It was still frozen for a while after your
testcase had ended (!), then caught up. Your mention of pinfo::init
and 'ps' along with my usage of 'top' leads me to think this may be
somehow related to the /proc filesystem.
Here's my humble contribution to the discussion:
~ time w
02:15:52 up 3 days, 20:34, 0 users, load average: 0.99, 0.62, 0.31
USER TTY LOGIN@ IDLE JCPU PCPU WHAT
real 0m0.203s <-- OK, nice and fast
user 0m0.077s
sys 0m0.139s
~ time strace -o w.out w
02:16:23 up 3 days, 20:34, 0 users, load average: 0.54, 0.55, 0.29
USER TTY LOGIN@ IDLE JCPU PCPU WHAT
real 0m28.487s <-- but stracing it is much, much slower
user 0m0.015s
sys 0m0.000s
The 'w' command is normally pretty fast. Running it under strace
makes it take an unreasonably long time. Something seems busted
somewhere. The strace output for this example has many occurrences of
~3.1-second delays that seem to occur as w is accumulating process
time information for all processes.
..mark
Thanks for the help Mark. My current suspicion is that the _pinfo isn't
getting initialized when the process is exec-ed by strace, but I haven't
proved that. I added a dump() member function to _pinfo, but it crashes
and I can't seem to debug that in gdb (it makes a stacktrace file
instead of letting me debug). So the cygpid.<n> shared object is there,
but I'm suspecting that it's either all zeros or just not fully
initialized -- and this is for the pid of the strace process. So for
each strace process, there's a 2-3 second delay when trying to read the
process list.
Daniel
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