Re: ntpd wedged by libc?

[Dave Hart <hart%ntp.org@localhost>]

On Wed, Mar 7, 2012 at 20:58, AGC <agcarver+netbsd%acarver.net@localhost> wrote:
> On 3/7/2012 09:14, Dave Hart wrote:
>> AGC, approximately how long does it take for ntpd to get wedged with
>> the latest libc?  And how many peers are there in your ntpq -p output?
>
> The wedge time has varied.  Sometimes it happened within a few hours of
> starting ntpd and other times it could take several days.  I could never
> really predict when it would fail.

You can probably speed it by pounding harder with ntpq.  Use ntpq's -n
option to take out any DNS-related delays, and sleep less between
queries.

> There are seven peers total listed in the billboard.

So about 50 ntpq-related %.3f snprintf() calls on the order of every 5 seconds.

> What about the log and statistics files?  I believe they're also using
> various printf() calls, too, yes?

Assuming you're not running ntpd interactively with -D or -d options
for debug trace output, clockstats, peerstats and loopstats would be
the next most frequent users of snprintf with floating point, but
that's a handful of floating-point-to-text conversions at the rate of
once per poll, or as often as 8 seconds for refclocks.  All the traces
you've provided have come through ntp_control.c indicating ntpq-style
NTP mode 6 queries triggered the failure.

Was ntpd using any CPU when it wedged?

Cheers,
Dave Hart