Running a large application that issues many gettimeofday()
system calls on a kernel running with notsc, results in time
slowing way down. I've seen the system time advance only
three minutes over a 30 minute period. The following program,
executed twice demonstrates the problem. Three instances running
in parallel made a 16 processor machine completely unusable.
#include <sys/time.h>
main()
{
struct timeval tv;
struct timezone tz;
while (1)
if (gettimeofday(&tv, &tz))
return;
}
I've recreated on 2.5.30, 2.5.44, and 2.5.47. Running a system that
is using the tsc I've tried 100 instances of this test running in
parallel with no problems - other than the normal incorrect time due
to tsc skew. At least no time slowdowns or hangs. The system I'm
using is a 4 node NUMAQ (x86) box.
I assume there is a lock starvation problem happening here, correct?
Any chance of fixing this?
--Michael Hohnbaum 503-578-5486 hohnbaum@us.ibm.com T/L 775-5486
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