Messages in this thread | | | Date | Fri, 21 May 1999 13:28:58 +0200 (CEST) | From | Andrea Arcangeli <> | Subject | Re: gettimeofday non-monotonic on 2.2.7 SMP |
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On Thu, 20 May 1999, dave madden wrote:
>I remember looking at that exact line, too, but I didn't notice the >error. Unfortunately, my userland prog still detects time decrements >in the 1-10ms range, frequently (but not always) accompanied by >recover_lost_timer messages in the log.
Do you still run xntpd? I tried to reproduce here with userspace and now that the `write' code got compiled from real, I can't reproduce the time-warp anymore. What I do is to run your gettimeofday checker in background and then I run two proggy that does a cli() and a loop for some time, and then sti(). Your proggy don't complain anymore here with the #if bug fixed. But I am not playing with settimeofday.
>This is frustrating: you'd think that more people would have noticed >this, but some people with SMP machines tried my program and nobody >reported any time warps. Maybe something's screwy with my hardware?
Because nobody has the CPU masked from userspace for more than 100msec.
>Looking at time.c now, I wonder if I've screwed up your patch >somehow. At line 484, I have: > > /* read Pentium cycle counter */ > rdtscl(last_tsc_low); > __asm__ __volatile__("rdtsc" : "=a" (last_tsc_low) : : "edx");
It's been a merging error. It make no one difference at all (except it's a bit slower :-). Anyway I fixed it now, next patches will be fixed. Thanks.
Andrea Arcangeli
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