netdev - Re: [net-next v1 PATCH 2/4] page_pool: add destroy attempts counter and rename tracepoint

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Date:   Sat, 16 Nov 2019 11:56:49 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     netdev@...r.kernel.org,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Matteo Croce <mcroce@...hat.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Tariq Toukan <tariqt@...lanox.com>, brouer@...hat.com
Subject: Re: [net-next v1 PATCH 2/4] page_pool: add destroy attempts counter
 and rename tracepoint

On Fri, 15 Nov 2019 17:33:18 +0100
Toke Høiland-Jørgensen <toke@...hat.com> wrote:

> Jesper Dangaard Brouer <brouer@...hat.com> writes:
> 
> > When Jonathan change the page_pool to become responsible to its
> > own shutdown via deferred work queue, then the disconnect_cnt
> > counter was removed from xdp memory model tracepoint.
> >
> > This patch change the page_pool_inflight tracepoint name to
> > page_pool_release, because it reflects the new responsability
> > better.  And it reintroduces a counter that reflect the number of
> > times page_pool_release have been tried.
> >
> > The counter is also used by the code, to only empty the alloc
> > cache once.  With a stuck work queue running every second and
> > counter being 64-bit, it will overrun in approx 584 billion
> > years. For comparison, Earth lifetime expectancy is 7.5 billion
> > years, before the Sun will engulf, and destroy, the Earth.  
> 
> I love how you just casually threw that last bit in there; and now I'm
> thinking about under which conditions that would not be enough. Maybe
> someone will put this code on a space probe bound for interstellar
> space, which will escape the death of our solar system only to be
> destined to increment this counter forever in the cold, dead void of
> space?

Like with performance numbers, when ever presenting a number, I always
strive to relate it some something else, as without that the number is
just a number.


> I think that is a risk we can live with, so:
> 
> Acked-by: Toke Høiland-Jørgensen <toke@...hat.com>

Thx

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer