Re: [dpdk-dev] [PATCH] Add user defined tag calculation callback to librte_distributor.

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

On Wed, Nov 05, 2014 at 03:30:37PM +0200, Qinglai Xiao wrote:
> User defined tag calculation has access to mbuf.
> Default tag is RSS hash result.
> 

Interesting idea.
Did you investigate was there any performance improvement or regression comparing 
whether the callback was called per-packet as packets were dequeued for distribution
(i.e. how you have things now in your patch), compared to calling
the callback in a loop to extract the tags for all packets initially? I suspect
there probably isn't much performance difference either way, but it may be worth
checking.
One other point, is that I think the callback to extract the tag should have
additional parameters - at least one, if not two. I would suggest that the
distributor pointer be passed in, as well as an arbitrary void * pointer.

Regards,
/Bruce

> Signed-off-by: Qinglai Xiao <jigsaw@gmail.com>
> ---
>  app/test/test_distributor.c              |    6 +++---
>  app/test/test_distributor_perf.c         |    2 +-
>  lib/librte_distributor/rte_distributor.c |   12 ++++++++++--
>  lib/librte_distributor/rte_distributor.h |    7 ++++++-
>  4 files changed, 20 insertions(+), 7 deletions(-)
> 
> diff --git a/app/test/test_distributor.c b/app/test/test_distributor.c
> index ce06436..6ea4943 100644
> --- a/app/test/test_distributor.c
> +++ b/app/test/test_distributor.c
> @@ -452,7 +452,7 @@ int test_error_distributor_create_name(void)
>  	char *name = NULL;
>  
>  	d = rte_distributor_create(name, rte_socket_id(),
> -			rte_lcore_count() - 1);
> +			rte_lcore_count() - 1, NULL);
>  	if (d != NULL || rte_errno != EINVAL) {
>  		printf("ERROR: No error on create() with NULL name param\n");
>  		return -1;
> @@ -467,7 +467,7 @@ int test_error_distributor_create_numworkers(void)
>  {
>  	struct rte_distributor *d = NULL;
>  	d = rte_distributor_create("test_numworkers", rte_socket_id(),
> -			RTE_MAX_LCORE + 10);
> +			RTE_MAX_LCORE + 10, NULL);
>  	if (d != NULL || rte_errno != EINVAL) {
>  		printf("ERROR: No error on create() with num_workers > MAX\n");
>  		return -1;
> @@ -515,7 +515,7 @@ test_distributor(void)
>  
>  	if (d == NULL) {
>  		d = rte_distributor_create("Test_distributor", rte_socket_id(),
> -				rte_lcore_count() - 1);
> +				rte_lcore_count() - 1, NULL);
>  		if (d == NULL) {
>  			printf("Error creating distributor\n");
>  			return -1;
> diff --git a/app/test/test_distributor_perf.c b/app/test/test_distributor_perf.c
> index b04864c..507e446 100644
> --- a/app/test/test_distributor_perf.c
> +++ b/app/test/test_distributor_perf.c
> @@ -227,7 +227,7 @@ test_distributor_perf(void)
>  
>  	if (d == NULL) {
>  		d = rte_distributor_create("Test_perf", rte_socket_id(),
> -				rte_lcore_count() - 1);
> +				rte_lcore_count() - 1, NULL);
>  		if (d == NULL) {
>  			printf("Error creating distributor\n");
>  			return -1;
> diff --git a/lib/librte_distributor/rte_distributor.c b/lib/librte_distributor/rte_distributor.c
> index 585ff88..78c92bd 100644
> --- a/lib/librte_distributor/rte_distributor.c
> +++ b/lib/librte_distributor/rte_distributor.c
> @@ -97,6 +97,7 @@ struct rte_distributor {
>  	union rte_distributor_buffer bufs[RTE_MAX_LCORE];
>  
>  	struct rte_distributor_returned_pkts returns;
> +	rte_distributor_tag_fn tag_cb;
>  };
>  
>  TAILQ_HEAD(rte_distributor_list, rte_distributor);
> @@ -267,6 +268,7 @@ rte_distributor_process(struct rte_distributor *d,
>  	struct rte_mbuf *next_mb = NULL;
>  	int64_t next_value = 0;
>  	uint32_t new_tag = 0;
> +	rte_distributor_tag_fn tag_cb = d->tag_cb;
>  	unsigned ret_start = d->returns.start,
>  			ret_count = d->returns.count;
>  
> @@ -282,7 +284,11 @@ 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);
> +			if (tag_cb) {
> +				new_tag = tag_cb(next_mb);
> +			} else {
> +				new_tag = (next_mb->hash.rss | 1);
> +			}
>  
>  			uint32_t match = 0;
>  			unsigned i;
> @@ -401,7 +407,8 @@ rte_distributor_clear_returns(struct rte_distributor *d)
>  struct rte_distributor *
>  rte_distributor_create(const char *name,
>  		unsigned socket_id,
> -		unsigned num_workers)
> +		unsigned num_workers,
> +		rte_distributor_tag_fn tag_cb)
>  {
>  	struct rte_distributor *d;
>  	struct rte_distributor_list *distributor_list;
> @@ -435,6 +442,7 @@ rte_distributor_create(const char *name,
>  	d = mz->addr;
>  	snprintf(d->name, sizeof(d->name), "%s", name);
>  	d->num_workers = num_workers;
> +	d->tag_cb = tag_cb;
>  
>  	rte_rwlock_write_lock(RTE_EAL_TAILQ_RWLOCK);
>  	TAILQ_INSERT_TAIL(distributor_list, d, next);
> diff --git a/lib/librte_distributor/rte_distributor.h b/lib/librte_distributor/rte_distributor.h
> index ec0d74a..844d325 100644
> --- a/lib/librte_distributor/rte_distributor.h
> +++ b/lib/librte_distributor/rte_distributor.h
> @@ -52,6 +52,9 @@ extern "C" {
>  
>  struct rte_distributor;
>  
> +typedef uint32_t (*rte_distributor_tag_fn)(struct rte_mbuf *);
> +/**< User defined tag calculation function */
> +
>  /**
>   * Function to create a new distributor instance
>   *
> @@ -65,12 +68,14 @@ struct rte_distributor;
>   * @param num_workers
>   *   The maximum number of workers that will request packets from this
>   *   distributor
> + * @param tag_cb
> + *   The callback function for calculation of user defined tag.
>   * @return
>   *   The newly created distributor instance
>   */
>  struct rte_distributor *
>  rte_distributor_create(const char *name, unsigned socket_id,
> -		unsigned num_workers);
> +		unsigned num_workers, rte_distributor_tag_fn tag_cb);
>  
>  /*  *** APIS to be called on the distributor lcore ***  */
>  /*
> -- 
> 1.7.1
>