Subject: Re: [RFC PATCH v3 00/14] Share events between metrics

From: Andi Kleen <[email-masked]>
Date: Fri, 8 May 2020 17:12:38 -0700

On Thu, May 07, 2020 at 10:36:15PM -0700, Ian Rogers wrote:
> Metric groups contain metrics. Metrics create groups of events to
> ideally be scheduled together. Often metrics refer to the same events,
> for example, a cache hit and cache miss rate. Using separate event
> groups means these metrics are multiplexed at different times and the
> counts don't sum to 100%. More multiplexing also decreases the
> accuracy of the measurement.
> 
> This change orders metrics from groups or the command line, so that
> the ones with the most events are set up first. Later metrics see if
> groups already provide their events, and reuse them if
> possible. Unnecessary events and groups are eliminated.

Yes some improvements here are great.

> 
> The option --metric-no-group is added so that metrics aren't placed in
> groups. This affects multiplexing and may increase sharing.
> 
> The option --metric-mo-merge is added and with this option the
> existing grouping behavior is preserved.

Could we also make this a per metric option, like

-M foo:nomerge,... 

or somesuch? Okay i suppose this could be a followon.

Ultimatively like you said we probably want to configure
defaults in the event file.

-Andi