Re: [dpdk-dev] [PATCH v2] mempool: replace c memcpy code semantics with optimized rte_memcpy

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

On Mon, May 30, 2016 at 10:45:11AM +0200, Olivier Matz wrote:
> Hi Jerin,
> 
> On 05/26/2016 10:07 AM, Jerin Jacob wrote:
> > Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> > ---
> > v1..v2
> > Corrected the the git commit message(s/mbuf/mempool/g)
> > ---
> >  lib/librte_mempool/rte_mempool.h | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/lib/librte_mempool/rte_mempool.h b/lib/librte_mempool/rte_mempool.h
> > index 60339bd..24876a2 100644
> > --- a/lib/librte_mempool/rte_mempool.h
> > +++ b/lib/librte_mempool/rte_mempool.h
> > @@ -73,6 +73,7 @@
> >  #include <rte_memory.h>
> >  #include <rte_branch_prediction.h>
> >  #include <rte_ring.h>
> > +#include <rte_memcpy.h>
> >  
> >  #ifdef __cplusplus
> >  extern "C" {
> > @@ -739,7 +740,6 @@ __mempool_put_bulk(struct rte_mempool *mp, void * const *obj_table,
> >  		    unsigned n, int is_mp)
> >  {
> >  	struct rte_mempool_cache *cache;
> > -	uint32_t index;
> >  	void **cache_objs;
> >  	unsigned lcore_id = rte_lcore_id();
> >  	uint32_t cache_size = mp->cache_size;
> > @@ -768,8 +768,7 @@ __mempool_put_bulk(struct rte_mempool *mp, void * const *obj_table,
> >  	 */
> >  
> >  	/* Add elements back into the cache */
> > -	for (index = 0; index < n; ++index, obj_table++)
> > -		cache_objs[index] = *obj_table;
> > +	rte_memcpy(&cache_objs[0], obj_table, sizeof(void *) * n);
> >  
> >  	cache->len += n;
> >  
> > 
> 
> I also checked in the get_bulk() function, which looks like that:
> 
> 	/* Now fill in the response ... */
> 	for (index = 0, len = cache->len - 1;
> 			index < n;
> 			++index, len--, obj_table++)
> 		*obj_table = cache_objs[len];
> 
> I think we could replace it by something like:
> 
> 	rte_memcpy(obj_table, &cache_objs[len - n], sizeof(void *) * n);
> 
> The only difference is that it won't reverse the pointers in the
> table, but I don't see any problem with that.
> 
> What do you think?

In true sense, it will _not_ be LIFO. Not sure about cache usage implications
on the specific use cases.

Jerin

> 
> 
> Regards,
> Olivier
>