Re: [PATCH] net/intel: allow fast-free to empty cache

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

On Mon, Mar 10, 2025 at 04:18:35PM +0100, Morten Brørup wrote:
> > From: Bruce Richardson [mailto:bruce.richardson@intel.com]
> > Sent: Monday, 10 March 2025 14.26
> > 
> > When freeing transmitted mbufs, there is no reason to send the freed
> > mbufs directly to the ring if the cache is empty - only if it is zero
> > size (in which case the cache pointer is NULL). Therefore, remove the
> > empty check and only check for a null cache pointer.
> > 
> > Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> > ---
> >  drivers/net/intel/common/tx.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/intel/common/tx.h
> > b/drivers/net/intel/common/tx.h
> > index d9cf4474fc..d361fe64ab 100644
> > --- a/drivers/net/intel/common/tx.h
> > +++ b/drivers/net/intel/common/tx.h
> > @@ -143,7 +143,7 @@ ci_tx_free_bufs_vec(struct ci_tx_queue *txq,
> > ci_desc_done_fn desc_done, bool ctx
> >  		void **cache_objs;
> >  		struct rte_mempool_cache *cache =
> > rte_mempool_default_cache(mp, rte_lcore_id());
> > 
> > -		if (!cache || cache->len == 0)
> > +		if (cache == NULL)
> >  			goto normal;
> > 
> >  		cache_objs = &cache->objs[cache->len];
> > --
> > 2.43.0
> 
> Yep, it did look strange.
> Reviewed-by: Morten Brørup <mb@smartsharesystems.com>
> 
Thanks for review.

FYI: Given that this is in a sensitive area and we are now past rc2, I'm going
to postponse merging this patch till 25.07, rather than risk it in 25.03.

/Bruce