lkml.org 
[lkml]   [2002]   [Nov]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Subjectgettimeofday() cripples notsc system
From
Date
John,

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

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:31    [from the cache]
©2003-2011 Jasper Spaans