Re: [PATCH v2] mm: emit tracepoint when RSS changes by threshold

From: Daniel Colascione
Date: Wed Sep 04 2019 - 13:18:14 EST

On Wed, Sep 4, 2019 at 8:38 AM Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> > but also for reducing
> > tracing noise. Flooding the traces makes it less useful for long traces and
> > post-processing of traces. IOW, the overhead reduction is a bonus.
> This is not really anything special for this tracepoint though.
> Basically any tracepoint in a hot path is in the same situation and I do
> not see a point why each of them should really invent its own way to
> throttle. Maybe there is some way to do that in the tracing subsystem
> directly.

I agree. I'd rather not special-case RSS in this way, especially not
with a hardcoded aggregation and thresholding configuration. It should
be possible to handle high-frequency trace data point aggregation in a
general way. Why shouldn't we be able to get a time series for, say,
dirty pages? Or various slab counts? IMHO, any counter on the system
ought to be observable in a uniform way.