Date: Wed, 11 Nov 1998 09:01:16 -0700 From: Wes Peters <wes@softweyr.com> To: Rasmus Kaj <kaj@interbizz.se> Cc: max@vega.pfts.com, freebsd-stable@FreeBSD.ORG Subject: Re: calcru: negative time of -71345076 usec for pid 23891 (make) Message-ID: <3649B4CC.ACF9587E@softweyr.com> References: <36440E77.3758284D@vega.pfts.com> <19981111004246Z.kaj@interbizz.se>
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Rasmus Kaj wrote:
>
> >>>>> "MS" == Maxim Sobolev <max@vega.pfts.com> writes:
>
> MS> Does anybody know what does this mysterious message means?
>
> MS> calcru: negative time of -71345076 usec for pid 23891 (make)
>
> Since I haven't seen an explanatory answer to this, let me throw in a
> guess (so there is at lest a try for an answer) ...
"Use the Source, Luke!"
wes@zaphod$ cd /usr/src/sys
wes@zaphod$ find . -name '*.c' -print | xargs grep "negative time"
./kern/kern_clock.c: printf("hzto: negative time difference %ld sec %ld usec\n",
./kern/kern_resource.c: printf("calcru: negative time: %ld usec\n", (long)totusec);
wes@zaphod$ vi kern/kern_resource.c
/*
* Transform the running time and tick information in proc p into user,
* system, and interrupt time usage.
*/
void
calcru(p, up, sp, ip)
...
if (p == curproc) {
/*
* Adjust for the current time slice. This is actually fairly
* important since the error here is on the order of a time
* quantum, which is much greater than the sampling error.
*/
microtime(&tv);
sec += tv.tv_sec - runtime.tv_sec;
usec += tv.tv_usec - runtime.tv_usec;
}
totusec = (quad_t)sec * 1000000 + usec;
if (totusec < 0) {
/* XXX no %qd in kernel. Truncate. */
printf("calcru: negative time: %ld usec\n", (long)totusec);
totusec = 0;
}
...
So, it looks like your process has been charged negative time during this
accounting interval. I've not studied the code to determine exactly *why*
this happens, or what it means, but it seems to be relatively harmless.
It started happening on my 486/66 server box around 2.2.5 release. I suspect
there may be a buglet in there somewhere, but it seems harmless so I just
avoid using ttyv0. ;^)
--
"Where am I, and what am I doing in this handbasket?"
Wes Peters Softweyr LLC
http://www.softweyr.com/~softweyr wes@softweyr.com
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