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

[Bruce Richardson <bruce.richardson-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

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;
> 
> 
>