On Fri, Jun 02, 2017 at 02:35:59PM +0300, Adrian Hunter wrote:
> On 01/06/17 16:11, Arnaldo Carvalho de Melo wrote:
> > Em Fri, May 26, 2017 at 02:31:40PM +0200, Jiri Olsa escreveu:
> >> The switch tracking test keeps failing on P4 cpu,
> >> when NMI watchdog is enabled.
> >>
> >> The reason is that P4 pmu uses substitute event for cycles
> >> when it's already taken (in our case by NMI watchdog), but
> >> this event does not give even results like cycles, and we
> >> could end up with no samples at all for our short
> >> measuring period.
>
> Did you consider increasing the measuring period?
not really, in some cases I saw no samples generated for bigger
periods for another workloads, so I did not think of that in here,
but I'll check
SNIP
> >>
> >> static int spin_sleep(void)
> >> {
> >> @@ -298,6 +299,27 @@ static int process_events(struct perf_evlist *evlist,
> >> return ret;
> >> }
> >>
> >> +static const char *get_hw_counter(void)
> >> +{
> >> + const char *counter = "cycles:u";
> >> + char *cpuid;
> >> +
> >> + cpuid = get_cpuid_str();
> >> +
> >> + /*
> >> + * P4 pmu uses substitute event for cycles if it's already
> >> + * taken, but it does not give even results like cycles,
> >> + * and we could end up with no samples at all for our short
> >> + * measuring period. Using "instructions:u" event instead,
> >> + * which seems to be stable enough.
> >> + */
> >> + if (!strcmp("GenuineIntel-15-4", cpuid))
>
> Why just model 4? Isn't all family 15 P4?
I thought there's just one model.. but just based on the kernel code
>
> >> + counter = "instructions:u";
> >> +
> >> + pr_debug("using '%s' HW counter");
>
> tests/switch-tracking.c: In function ‘get_hw_counter’:
> tests/switch-tracking.c:319:2: error: format ‘%s’ expects a matching ‘char
> *’ argument [-Werror=format=]
omg.. sure ;-)
thanks,
jirka
