----- Original Message ----
> From: "Escobio, Roger " <[EMAIL PROTECTED]>
> To: Bernard Li <[EMAIL PROTECTED]>
> Cc: [EMAIL PROTECTED]
> Sent: Wednesday, September 10, 2008 9:19:47 PM
> Subject: Re: [Ganglia-general] Anyone experience petabyte peaks in network
> metric in ganglia 3.x.y ?
>
>
>
> > -----Original Message-----
> > From: Bernard Li [mailto:[EMAIL PROTECTED]
> > Sent: September 10, 2008 3:05 PM
> > To: Escobio, Roger [CMB-IT]
> > Cc: [EMAIL PROTECTED]
> > Subject: Re: [Ganglia-general] Anyone experience petabyte
> > peaks in network metric in ganglia 3.x.y ?
> >
> > Hi Roger:
> >
> > On Wed, Sep 10, 2008 at 11:52 AM, Martin Knoblauch
> > wrote:
> >
> > >> I created a patch again linux/metrics.c (3.1.1 version) to add the
> > >> counterdiff function found in *bsd/metrics.c
> > >> Are you interested in it? Just let me know and I'll send
> > it to the list
> > >>
> > >
> > > Yes please. I am definitely like to have a look at your patch.
> >
> > In case the patch is too large to be sent to the mailing-list, you
> > could also file a bug and upload the patch via bugzilla.ganglia.info.
>
> Well, is not big
> As I said, it is just a copy paste from *bsd code , so not big deal :-)
>
> But at least compile and not coredump gmond in our linux :-)
>
Roger, [changed Mailing List to ganglia-developers]
just to understand things right, your patch is only a code cleanup and you
still need the "#ifdef REMOVE_BOGUS_SPIKES" to get rid of the spikes. Correct?
Some comments on the patch:
>--- libmetrics/linux/metrics.c-ori 2008-09-09 18:54:40.000000000 +0000
>+++ libmetrics/linux/metrics.c 2008-09-09 19:09:44.000000000 +0000
>@@ -222,40 +222,20 @@
> if ( !ns ) return;
>
> rbi = strtoul( p, &p ,10);
>- if ( rbi >= ns->rbi ) {
>- l_bytes_in += rbi - ns->rbi;
>- } else {
>- debug_msg("update_ifdata(%s) - Overflow in rbi: %lu ->
>%lu",caller,ns->rbi,rbi);
>- l_bytes_in += ULONG_MAX - ns->rbi + rbi;
>- }
>+ l_bytes_in = counterdiff(rbi,ns->rbi,ULONG_MAX, 0);
Shouldn't that be "+= counterdiff/..."? l_bytes_in is cummulated over all NICs.
> ns->rbi = rbi;
>
> rpi = strtoul( p, &p ,10);
>- if ( rpi >= ns->rpi ) {
>- l_pkts_in += rpi - ns->rpi;
>- } else {
>- debug_msg("updata_ifdata(%s) - Overflow in rpi: %lu ->
>%lu",caller,ns->rpi,rpi);
>- l_pkts_in += ULONG_MAX - ns->rpi + rpi;
>- }
>+ l_pkts_in = counterdiff(rpi,ns->rpi,ULONG_MAX, 0);
ditto
> ns->rpi = rpi;
>
> for (i = 0; i < 6; i++) strtol(p, &p, 10);
> rbo = strtoul( p, &p ,10);
>- if ( rbo >= ns->rbo ) {
>- l_bytes_out += rbo - ns->rbo;
>- } else {
>- debug_msg("update_ifdata(%s) - Overflow in rbo: %lu ->
>%lu",caller,ns->rbo,rbo);
>- l_bytes_out += ULONG_MAX - ns->rbo + rbo;
>- }
>+ l_bytes_out = counterdiff(rbo,ns->rbo,ULONG_MAX, 0);
ditto
> ns->rbo = rbo;
>
> rpo = strtoul( p, &p ,10);
>- if ( rpo >= ns->rpo ) {
>- l_pkts_out += rpo - ns->rpo;
>- } else {
>- debug_msg("update_ifdata(%s) - Overflow in rpo: %lu ->
>%lu",caller,ns->rpo,rpo);
>- l_pkts_out += ULONG_MAX - ns->rpo + rpo;
>- }
>+ l_pkts_out = counterdiff(rpo,ns->rpo,ULONG_MAX, 0);
ditto
> ns->rpo = rpo;
> }
> p = index (p, '\n') + 1; // skips a line
>@@ -1305,3 +1285,40 @@
> val.f = most_full;
> return val;
> }
>+
>+static unsigned long
>+counterdiff(unsigned long oldval, unsigned long newval, unsigned long maxval,
>unsigned long maxdiff)
>+{
>+ unsigned long diff;
>+
>+ if (maxdiff == 0)
>+ maxdiff = maxval;
>+
>+ /* Paranoia */
>+ if (oldval > maxval || newval > maxval)
>+ return 0;
Really cannot happen with maxval being ULONG_MAX. Even the paranoid should feel
safe here :-)
>+
>+ /*
>+ * Tackle the easy case. Don't worry about maxdiff here because
>+ * we're SOL if it happens (i.e. assuming a reset just makes
>+ * matters worse).This
>+ */
>+ if (oldval <= newval)
>+ return (newval - oldval);
>+
>+ /*
>+ * Now the tricky part. If we assume counters never get reset,
>+ * this is easy. Unfortunaly, they do get reset on some
>+ * systems, so we need to try and deal with that. Our huristic
>+ * is that if out difference is greater then maxdiff and newval
>+ * is less or equal to maxdiff, then we've probably been reset
>+ * rather then actually wrapping. Obviously, you need to be
>+ * careful to poll often enough that you won't exceed maxdiff or
>+ * you will get undersized numbers when you do wrap.
>+ */
>+ diff = maxval - oldval + newval;
>+ if (diff > maxdiff && newval <= maxdiff)
>+ return newval;
"diff > maxdiff" cannot happen, as maxdiff is ULONG_MAX
>+
>+ return diff;
>+}
Otherwise one could accept the patch, because it reduces code-duplication.
Cheers
Martin
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