2003-05-29 23:27:04

by Michael Griffith

[permalink] [raw]
Subject: nfsstat printing overflow

A small patch to handle when the RPC call counts are > 2^32/100.

--
Michael A. Griffith
<[email protected]>
408-907-2151
650-292-1516


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2003-05-30 05:43:18

by NeilBrown

[permalink] [raw]
Subject: Re: nfsstat printing overflow

On Thursday May 29, [email protected] wrote:
> A small patch to handle when the RPC call counts are > 2^32/100.
>
Thanks.
However:

> + unsigned long long pct;

> + for (j = 0; j < 6 && i + j < nr; j++) {
> + pct = ((unsigned long long) info[i+j]*100)/total;
> + printf("%-6d %2d%% ", info[i+j], pct);
> + }

if pct is an "unsigned long long" we should use "%llu" to print it.

The following patch has been commited to the nfs-utils CVS and will be
in the next release, which will probably be 1.1.0

NeilBrown

Index: ChangeLog
===================================================================
RCS file: /cvsroot/nfs/nfs-utils/ChangeLog,v
retrieving revision 1.202
diff -u -r1.202 ChangeLog
--- ChangeLog 30 May 2003 05:16:52 -0000 1.202
+++ ChangeLog 30 May 2003 05:38:44 -0000
@@ -1,3 +1,9 @@
+2003-05-30 Michael Griffith <[email protected]>
+ NeilBrown <[email protected]>
+
+ utils/nfsstat/nfsstat.c(print_callstats): use unsigned
+ long long to avoid overflow when printing stats.
+
2003-05-30 NeilBrown <[email protected]>

* support/export/export.c, support/include/nfslib.h,
Index: utils/nfsstat/nfsstat.c
===================================================================
RCS file: /cvsroot/nfs/nfs-utils/utils/nfsstat/nfsstat.c,v
retrieving revision 1.4
diff -u -r1.4 nfsstat.c
--- utils/nfsstat/nfsstat.c 5 May 2002 23:33:30 -0000 1.4
+++ utils/nfsstat/nfsstat.c 30 May 2003 05:38:46 -0000
@@ -307,7 +307,8 @@
print_callstats(const char *hdr, const char **names,
unsigned int *info, unsigned int nr)
{
- unsigned int total;
+ unsigned long long total;
+ unsigned long long pct;
int i, j;

fputs(hdr, stdout);
@@ -319,9 +320,10 @@
for (j = 0; j < 6 && i + j < nr; j++)
printf("%-11s", names[i+j]);
printf("\n");
- for (j = 0; j < 6 && i + j < nr; j++)
- printf("%-6d %2d%% ",
- info[i+j], 100 * info[i+j] / total);
+ for (j = 0; j < 6 && i + j < nr; j++) {
+ pct = ((unsigned long long) info[i+j]*100)/total;
+ printf("%-6d %2llu%% ", info[i+j], pct);
+ }
printf("\n");
}
printf("\n");


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2003-06-02 07:10:24

by Greg Lindahl

[permalink] [raw]
Subject: Re: Re: nfsstat printing overflow

On Fri, May 30, 2003 at 03:43:00PM +1000, Neil Brown wrote:
> On Thursday May 29, [email protected] wrote:
> > A small patch to handle when the RPC call counts are > 2^32/100.
> >
> Thanks.
> However:
>
> > + unsigned long long pct;
>
> > + for (j = 0; j < 6 && i + j < nr; j++) {
> > + pct = ((unsigned long long) info[i+j]*100)/total;
> > + printf("%-6d %2d%% ", info[i+j], pct);
> > + }

It feels like overkill to use long long for this when you can get
just as good of behavior with:

unsigned long toto100;

if (total >= 100)
toto100 = total / 100;
else
toto100 = 1;

for (j = 0; j < 6 && i + j < nr; j++)
printf("%-6d %2d%% ", info[i+j], info[i+j]/toto100);

In both pieces of code, if total overflows you get the wrong answer. So you
didn't get much of a benefit from the long long.

If you care about getting the %s reasonable when total is small, you can
move the if() inside the for().

Doesn't gcc inline code on archs without real 64-bit ops? Yech.

greg



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