Re: [dpdk-dev] 答复: [PATCH] Add user defined tag calculation callback tolibrte_distributor.

[Bruce Richardson <bruce.richardson@intel.com>]

On Fri, Nov 07, 2014 at 04:52:46PM +0200, jigsaw wrote:
> Yeah that's better. As below, right?

Yep.

> 
> @@ -290,6 +294,7 @@ rte_distributor_process(struct rte_distributor *d,
>                                 match |= (!(d->in_flight_tags[i] ^ new_tag)
>                                         << i);
> 
> +                       match &= d->in_flight_bitmask;
>                         if (match) {
>                                 next_mb = NULL;
>                                 unsigned worker = __builtin_ctz(match);
> 
> 
> On Fri, Nov 7, 2014 at 4:44 PM, Bruce Richardson <bruce.richardson@intel.com
> > wrote:
> 
> > On Fri, Nov 07, 2014 at 04:31:18PM +0200, jigsaw wrote:
> > > Hi Bruce,
> > >
> > > Pls have a quick look at the diff to see if this is exactly what you mean
> > > about the bitmask.
> > > I just wrote it without even compiling, just to express the idea. So it
> > may
> > > leave some places unpatched.
> > > If this is agreed, I will make a decent test to verify it before sending
> > > the patch for RFC.
> > >
> > > diff --git a/lib/librte_distributor/rte_distributor.c
> > > b/lib/librte_distributor/rte_di
> > > index 585ff88..d606bcf 100644
> > > --- a/lib/librte_distributor/rte_distributor.c
> > > +++ b/lib/librte_distributor/rte_distributor.c
> > > @@ -92,6 +92,8 @@ struct rte_distributor {
> > >         unsigned num_workers;                 /**< Number of workers
> > > polling */
> > >
> > >         uint32_t in_flight_tags[RTE_MAX_LCORE];
> > > +       uint32_t in_flight_bitmask;
> > > +
> > >         struct rte_distributor_backlog backlog[RTE_MAX_LCORE];
> > >
> > >         union rte_distributor_buffer bufs[RTE_MAX_LCORE];
> > > @@ -188,6 +190,7 @@ static inline void
> > >  handle_worker_shutdown(struct rte_distributor *d, unsigned wkr)
> > >  {
> > >         d->in_flight_tags[wkr] = 0;
> > > +       d->in_flight_mask &= ~(1 << wkr);
> > >         d->bufs[wkr].bufptr64 = 0;
> > >         if (unlikely(d->backlog[wkr].count != 0)) {
> > >                 /* On return of a packet, we need to move the
> > > @@ -241,6 +244,7 @@ process_returns(struct rte_distributor *d)
> > >                         else {
> > >                                 d->bufs[wkr].bufptr64 =
> > RTE_DISTRIB_GET_BUF;
> > >                                 d->in_flight_tags[wkr] = 0;
> > > +                               d->in_flight_mask &= ~(1 << wkr);
> > >                         }
> > >                         oldbuf = data >> RTE_DISTRIB_FLAG_BITS;
> > >                 } else if (data & RTE_DISTRIB_RETURN_BUF) {
> > > @@ -282,12 +286,13 @@ rte_distributor_process(struct rte_distributor *d,
> > >                         next_mb = mbufs[next_idx++];
> > >                         next_value = (((int64_t)(uintptr_t)next_mb)
> > >                                         << RTE_DISTRIB_FLAG_BITS);
> > > -                       new_tag = (next_mb->hash.rss | 1);
> > > +                       new_tag = next_mb->hash.rss;
> > >
> > >                         uint32_t match = 0;
> > >                         unsigned i;
> > >                         for (i = 0; i < d->num_workers; i++)
> > > -                               match |= (!(d->in_flight_tags[i] ^
> > new_tag)
> > > +                               match |= (((!(d->in_flight_tags[i] ^
> > > new_tag)) &
> > > +                                               (d->in_flight_bitmask >>
> > i))
> >
> > I would not do the bitmask comparison here, as that's extra instruction in
> > the
> > loop. Instead, because its a bitmask, build up the match variable as it was
> > before, and then just do a single and operation afterwards, outside the
> > loop
> > body.
> >
> > /Bruce
> >
> > >                                         << i);
> > >
> > >                         if (match) {
> > > @@ -309,6 +314,7 @@ rte_distributor_process(struct rte_distributor *d,
> > >                         else {
> > >                                 d->bufs[wkr].bufptr64 = next_value;
> > >                                 d->in_flight_tags[wkr] = new_tag;
> > > +                               d->in_flight_bitmask |= 1 << wkr;
> > >                                 next_mb = NULL;
> > >                         }
> > >                         oldbuf = data >> RTE_DISTRIB_FLAG_BITS;
> > >
> > >
> > >
> >