Re: [PATCH v7 3/3] KVM: perf: kvm events analysis tool

[don]

ä 2012å08æ27æ 23:53, Andrew Jones åé:
> On Mon, Aug 27, 2012 at 05:51:46PM +0800, Dong Hao wrote:
>
> <snip>
>
> > +struct event_stats {
> > +	u64 count;
> > +	u64 time;
> > +
> > +	/* used to calculate stddev. */
> > +	double mean;
> > +	double M2;
> > +};
> How about moving the stats functions from builtin-stat.c to e.g.
> util/stats.c, and then reusing them? Then this struct (which I would
> rename to kvm_event_stats) would look like this
>
> struct kvm_event_stats {
>          u64 time;
>          struct stats stats;
> };
>
> of course the get_event_ accessor generators would need tweaking
>
> <snip>
>
> > +static void update_event_stats(struct event_stats *stats, u64 time_diff)
> > +{
> > +	double delta;
> > +
> > +	stats->count++;
> > +	stats->time += time_diff;
> > +
> > +	delta = time_diff - stats->mean;
> > +	stats->mean += delta / stats->count;
> > +	stats->M2 += delta*(time_diff - stats->mean);
> > +}
> Reusing stats would allow this to become just
>
> static void update_event_stats(struct kvm_event_stats *stats, u64 time_diff)
> {
> 	update_stats(&kvm_stats->stats, time_diff);
> 	kvm_stats->time += time_diff;
> }
>
> > +
> > +static double event_stats_stddev(int vcpu_id, struct kvm_event *event)
> > +{
> > +	struct event_stats *stats = &event->total;
> > +	double variance, variance_mean, stddev;
> > +
> > +	if (vcpu_id != -1)
> > +		stats = &event->vcpu[vcpu_id];
> > +
> > +	BUG_ON(!stats->count);
> > +
> > +	variance = stats->M2 / (stats->count - 1);
> > +	variance_mean = variance / stats->count;
> > +	stddev = sqrt(variance_mean);
> > +
> > +	return stddev * 100 / stats->mean;
> This function's name implies it returns the stddev, but it returns the
> relative stddev instead. Maybe rename it? This would be simplified
> with code reuse too to basically just
>
> return stddev_stats(&kvm_stats->stats) * 100 / kvm_stats->stats.mean;
>
> Drew
Sorry for my late response, Andrew and thank you very much for your 
comments. We will try
to realize it in our next version.

Thanks,
Dong

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/