netdev - Re: [RFC net-next 2/2] net: mvneta: add support for page_pool_get

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Date:   Thu, 7 Apr 2022 21:25:50 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Ilias Apalodimas <ilias.apalodimas@...aro.org>
Cc:     Lorenzo Bianconi <lorenzo@...nel.org>, netdev@...r.kernel.org,
        lorenzo.bianconi@...hat.com, davem@...emloft.net, kuba@...nel.org,
        pabeni@...hat.com, thomas.petazzoni@...tlin.com,
        jbrouer@...hat.com, jdamato@...tly.com
Subject: Re: [RFC net-next 2/2] net: mvneta: add support for
 page_pool_get_stats

On Thu, Apr 07, 2022 at 09:35:52PM +0300, Ilias Apalodimas wrote:
> Hi Andrew,
> 
> On Thu, 7 Apr 2022 at 21:25, Andrew Lunn <andrew@...n.ch> wrote:
> >
> > > +static void mvneta_ethtool_pp_stats(struct mvneta_port *pp, u64 *data)
> > > +{
> > > +     struct page_pool_stats stats = {};
> > > +     int i;
> > > +
> > > +     for (i = 0; i < rxq_number; i++) {
> > > +             struct page_pool *page_pool = pp->rxqs[i].page_pool;
> > > +             struct page_pool_stats pp_stats = {};
> > > +
> > > +             if (!page_pool_get_stats(page_pool, &pp_stats))
> > > +                     continue;
> > > +
> > > +             stats.alloc_stats.fast += pp_stats.alloc_stats.fast;
> > > +             stats.alloc_stats.slow += pp_stats.alloc_stats.slow;
> > > +             stats.alloc_stats.slow_high_order +=
> > > +                     pp_stats.alloc_stats.slow_high_order;
> > > +             stats.alloc_stats.empty += pp_stats.alloc_stats.empty;
> > > +             stats.alloc_stats.refill += pp_stats.alloc_stats.refill;
> > > +             stats.alloc_stats.waive += pp_stats.alloc_stats.waive;
> > > +             stats.recycle_stats.cached += pp_stats.recycle_stats.cached;
> > > +             stats.recycle_stats.cache_full +=
> > > +                     pp_stats.recycle_stats.cache_full;
> > > +             stats.recycle_stats.ring += pp_stats.recycle_stats.ring;
> > > +             stats.recycle_stats.ring_full +=
> > > +                     pp_stats.recycle_stats.ring_full;
> > > +             stats.recycle_stats.released_refcnt +=
> > > +                     pp_stats.recycle_stats.released_refcnt;
> >
> > We should be trying to remove this sort of code from the driver, and
> > put it all in the core.  It wants to be something more like:
> >
> >         struct page_pool_stats stats = {};
> >         int i;
> >
> >         for (i = 0; i < rxq_number; i++) {
> >                 struct page_pool *page_pool = pp->rxqs[i].page_pool;
> >
> >                 if (!page_pool_get_stats(page_pool, &stats))
> >                         continue;
> >
> >         page_pool_ethtool_stats_get(data, &stats);
> >
> > Let page_pool_get_stats() do the accumulate as it puts values in stats.
> 
> Unless I misunderstand this, I don't think that's doable in page pool.
> That means page pool is aware of what stats to accumulate per driver
> and I certainly don't want anything driver specific to creep in there.
> The driver knows the number of pools he is using and he can gather
> them all together.

I agree that the driver knows about the number of pools. For mvneta,
there is one per RX queue. Which is this part of my suggestion

> >         for (i = 0; i < rxq_number; i++) {
> >                 struct page_pool *page_pool = pp->rxqs[i].page_pool;
> >

However, it has no idea about the stats themselves. They are purely a
construct of the page pool. Hence the next part of my suggest, ask the
page pool for the stats, place them into stats, doing the accumulate
at the same time.:

> >                 if (!page_pool_get_stats(page_pool, &stats))
> >                         continue;

and now we have the accumulated stats, turn them into ethtool format:

> >         page_pool_ethtool_stats_get(data, &stats);

Where do you see any driver knowledge required in either of
page_pool_get_stats() or page_pool_ethtool_stats_get().

      Andrew