rrdtool / mtr causing stalling on 7.0

Sun Mar 9 01:14:17 UTC 2008

----- Original Message ----- 
From: "Robert Watson" <rwatson at FreeBSD.org>
> It looks like the attachment got lost on the way through the mailing list.
> 
> I think the first starting point is: what sort of stall is this?  Is it, for 
> example, all network communication stalling, all disk I/O stalling, or the 
> entire kernel and all processes stalling?  The usual diagnostics are:
> 
> - Does the machine stop responding to pings while stalled, and/or possibly
>   "catch up" all at once when it recovers?
> 
> - If you run the following loop on the machine without any network or console
>   I/O, do you see gaps in time stamps:
> 
>  while (1) {
>  sleep 1
>  date >> date.log
>  }
> 
> - If you write a short C program that looks a lot like the above loop, but
>   logs time stamps into an in-memory buffer, and have it look for gaps in the
>   sequence of >3 seconds, does it run across the stall?

Thanks for the ideas Robert the output from the shell script
this shows significant gaps:-
Sun Mar  9 00:20:33 GMT 2008
Sun Mar  9 00:20:34 GMT 2008 <== Stall
Sun Mar  9 00:21:09 GMT 2008
Sun Mar  9 00:21:10 GMT 2008
...
Sun Mar  9 00:25:23 GMT 2008
Sun Mar  9 00:25:24 GMT 2008
Sun Mar  9 00:25:25 GMT 2008
Sun Mar  9 00:25:27 GMT 2008 <== Stall
Sun Mar  9 00:25:53 GMT 2008
Sun Mar  9 00:25:59 GMT 2008
Sun Mar  9 00:26:00 GMT 2008

Running a ping along side shows no missed responses.

Enabling lock profiling for the period changes the behaviour somewhat,
producing shorter but multiple stalls.

Sun Mar  9 00:30:31 GMT 2008
Sun Mar  9 00:30:32 GMT 2008
Sun Mar  9 00:30:34 GMT 2008
Sun Mar  9 00:30:35 GMT 2008
Sun Mar  9 00:30:36 GMT 2008
Sun Mar  9 00:30:37 GMT 2008
Sun Mar  9 00:30:38 GMT 2008
Sun Mar  9 00:30:41 GMT 2008
Sun Mar  9 00:30:42 GMT 2008 <== Stall
Sun Mar  9 00:30:44 GMT 2008
Sun Mar  9 00:30:45 GMT 2008 <== Stall
Sun Mar  9 00:30:47 GMT 2008 <== Stall
Sun Mar  9 00:30:49 GMT 2008
Sun Mar  9 00:30:50 GMT 2008 <== Stall
Sun Mar  9 00:30:52 GMT 2008 <== Stall
Sun Mar  9 00:30:54 GMT 2008
Sun Mar  9 00:30:55 GMT 2008
Sun Mar  9 00:30:56 GMT 2008
Sun Mar  9 00:30:57 GMT 2008 <== Stall
Sun Mar  9 00:31:03 GMT 2008 <== Stall
Sun Mar  9 00:31:05 GMT 2008
Sun Mar  9 00:31:06 GMT 2008 <== Stall
Sun Mar  9 00:31:08 GMT 2008
Sun Mar  9 00:31:09 GMT 2008
Sun Mar  9 00:31:10 GMT 2008
Sun Mar  9 00:31:11 GMT 2008 <== Stall
Sun Mar  9 00:31:14 GMT 2008
Sun Mar  9 00:31:15 GMT 2008
Sun Mar  9 00:31:16 GMT 2008 <== Stall
Sun Mar  9 00:31:20 GMT 2008
Sun Mar  9 00:31:21 GMT 2008
Sun Mar  9 00:31:22 GMT 2008

Using the following c code we also see stalls:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main( char **argv, int argc )
{
    time_t last = time( NULL );
    while ( 1 )
    {
        time_t now = time( NULL );
        time_t diff = now - last;
        if ( diff >= 2 )
        {
            fprintf( stderr, "stalled for %d seconds\n", diff );
        }
        fprintf( stderr, ctime( &now ) );
        last = now;
        sleep( 1 );
    }

    exit( 0 );
}

[date.log]
Sun Mar  9 00:55:40 GMT 2008
Sun Mar  9 00:55:43 GMT 2008 <== Stall
Sun Mar  9 00:56:11 GMT 2008
Sun Mar  9 00:56:12 GMT 2008
Sun Mar  9 00:56:13 GMT 2008
Sun Mar  9 00:56:14 GMT 2008
Sun Mar  9 00:56:15 GMT 2008
[/date.log]

[timec output]
Sun Mar  9 00:55:40 2008
Sun Mar  9 00:55:41 2008
Sun Mar  9 00:55:42 2008
stalled for 2 seconds
Sun Mar  9 00:55:44 2008
stalled for 5 seconds
Sun Mar  9 00:55:49 2008
stalled for 2 seconds
Sun Mar  9 00:55:51 2008
stalled for 2 seconds
Sun Mar  9 00:55:53 2008
Sun Mar  9 00:55:54 2008
Sun Mar  9 00:55:55 2008
Sun Mar  9 00:55:56 2008
Sun Mar  9 00:55:57 2008
Sun Mar  9 00:55:58 2008
Sun Mar  9 00:55:59 2008
Sun Mar  9 00:56:00 2008
Sun Mar  9 00:56:01 2008
Sun Mar  9 00:56:02 2008
Sun Mar  9 00:56:03 2008
Sun Mar  9 00:56:04 2008
Sun Mar  9 00:56:05 2008
Sun Mar  9 00:56:06 2008
Sun Mar  9 00:56:07 2008
Sun Mar  9 00:56:08 2008
Sun Mar  9 00:56:09 2008
Sun Mar  9 00:56:10 2008
Sun Mar  9 00:56:11 2008
Sun Mar  9 00:56:12 2008
Sun Mar  9 00:56:13 2008
Sun Mar  9 00:56:14 2008
Sun Mar  9 00:56:15 2008
[/timec output]

As the list ate the attachment, the output from the lock profile
can be found here:-
ftp://ftp1.multiplay.co.uk/pub/other/freebsd-7.0-rrdtool-stall.zip

    Regards
    Steve

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