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

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

On Tue, May 24, 2016 at 04:59:47PM +0200, Olivier Matz wrote:
> Hi Jerin,
> 
> 
> On 05/24/2016 04:50 PM, Jerin Jacob wrote:
> > Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> > ---
> >  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 ed2c110..ebe399a 100644
> > --- a/lib/librte_mempool/rte_mempool.h
> > +++ b/lib/librte_mempool/rte_mempool.h
> > @@ -74,6 +74,7 @@
> >  #include <rte_memory.h>
> >  #include <rte_branch_prediction.h>
> >  #include <rte_ring.h>
> > +#include <rte_memcpy.h>
> >  
> >  #ifdef __cplusplus
> >  extern "C" {
> > @@ -917,7 +918,6 @@ __mempool_put_bulk(struct rte_mempool *mp, void * const *obj_table,
> >  		    unsigned n, __rte_unused 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;
> > @@ -946,8 +946,7 @@ __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;
> >  
> > 
> 
> The commit title should be "mempool" instead of "mbuf".

I will fix it.

> Are you seeing some performance improvement by using rte_memcpy()?

Yes, In some case, In default case, It was replaced with memcpy by the
compiler itself(gcc 5.3). But when I tried external mempool manager patch and
then performance dropped almost 800Kpps. Debugging further it turns out that
external mempool managers unrelated change was knocking out the memcpy.
explicit rte_memcpy brought back 500Kpps. Remaing 300Kpps drop is still
unknown(In my test setup, packets are in the local cache, so it must be
something do with __mempool_put_bulk text alignment change or similar.

Anyone else observed performance drop with external poolmanager?

Jerin

> 
> Regards
> Olivier