[EXT] [RFC, v1 4/6] graph: enhance graph walk by cross-core dispatch

[Yan, Zhirun]

> -----Original Message-----
> From: Pavan Nikhilesh Bhagavatula <pbhagavatula at marvell.com>
> Sent: Thursday, September 8, 2022 1:27 PM
> To: Yan, Zhirun <zhirun.yan at intel.com>; dev at dpdk.org; Jerin Jacob
> Kollanukkaran <jerinj at marvell.com>; Kiran Kumar Kokkilagadda
> <kirankumark at marvell.com>
> Cc: Liang, Cunming <cunming.liang at intel.com>; Wang, Haiyue
> <haiyue.wang at intel.com>
> Subject: RE: [EXT] [RFC, v1 4/6] graph: enhance graph walk by cross-core
> dispatch
> 
> > This patch enhance the task scheduler mechanism to enable dispatching
> > tasks to another worker cores. Currently, there is only a local work
> > queue for one graph to walk. We introduce a scheduler worker queue in
> > each worker core for dispatching tasks. It will perform the walk on
> > scheduler work queue first, then handle the local work queue.
> >
> > Signed-off-by: Haiyue Wang <haiyue.wang at intel.com>
> > Signed-off-by: Cunming Liang <cunming.liang at intel.com>
> > Signed-off-by: Zhirun Yan <zhirun.yan at intel.com>
> > ---
> >  lib/graph/graph.c            |  6 ++++++
> >  lib/graph/rte_graph_worker.h | 11 +++++++++++
> >  2 files changed, 17 insertions(+)
> >
> > diff --git a/lib/graph/graph.c b/lib/graph/graph.c index
> > b4eb18175a..49ea2b3fbb 100644
> > --- a/lib/graph/graph.c
> > +++ b/lib/graph/graph.c
> > @@ -368,6 +368,8 @@ rte_graph_destroy(rte_graph_t id)
> >  	while (graph != NULL) {
> >  		tmp = STAILQ_NEXT(graph, next);
> >  		if (graph->id == id) {
> > +			/* Destroy the schedule work queue if has */
> > +			graph_sched_wq_destroy(graph);
> >  			/* Call fini() of the all the nodes in the graph */
> >  			graph_node_fini(graph);
> >  			/* Destroy graph fast path memory */ @@ -470,6 +472,10
> @@
> > graph_clone(struct graph *parent_graph, const char *name,
> >  	if (graph_node_init(graph))
> >  		goto graph_mem_destroy;
> >
> > +	/* Create the graph schedule work queue */
> > +	if (graph_sched_wq_create(graph, parent_graph))
> > +		goto graph_mem_destroy;
> > +
> >  	/* All good, Lets add the graph to the list */
> >  	graph_id++;
> >  	STAILQ_INSERT_TAIL(&graph_list, graph, next); diff --git
> > a/lib/graph/rte_graph_worker.h b/lib/graph/rte_graph_worker.h index
> > faf3f31ddc..e98697d880 100644
> > --- a/lib/graph/rte_graph_worker.h
> > +++ b/lib/graph/rte_graph_worker.h
> > @@ -177,6 +177,7 @@ static inline void  rte_graph_walk(struct
> > rte_graph *graph)  {
> >  	const rte_graph_off_t *cir_start = graph->cir_start;
> > +	const unsigned int lcore_id = graph->lcore_id;
> >  	const rte_node_t mask = graph->cir_mask;
> >  	uint32_t head = graph->head;
> >  	struct rte_node *node;
> > @@ -184,6 +185,9 @@ rte_graph_walk(struct rte_graph *graph)
> >  	uint16_t rc;
> >  	void **objs;
> >
> > +	if (graph->wq != NULL)
> > +		__rte_graph_sched_wq_process(graph);
> > +
> 
> 
> We should introduce a flags field in rte_graph_param which can be used by
> the application to define whether a graph should support multi-core
> dispatch.
> 
Yes, I will add a flags field in next version.

> Then we can make `__rte_graph_sched_wq_process` as node 0 during graph
> creation so that it will be always called at the start of graph processing
> followed by calling rest of the nodes.
> This will remove unnecessary branches in fastpath.
> 

Thanks for your comments and sorry for my late reply.
Yes, we can make `__rte_graph_sched_wq_process` as node 0 with dispatch flags.
But I am not sure whether we need to register a new node here. It means we should change
the graph topo, and it will be an isolated node with no links.


> >  	/*
> >  	 * Walk on the source node(s) ((cir_start - head) -> cir_start) and
> > then
> >  	 * on the pending streams (cir_start -> (cir_start + mask) ->
> > cir_start) @@ -205,6 +209,12 @@ rte_graph_walk(struct rte_graph
> *graph)
> >  		objs = node->objs;
> >  		rte_prefetch0(objs);
> >
> > +		/* Schedule the node until all task/objs are done */
> > +		if (node->lcore_id != RTE_MAX_LCORE && (int32_t)head > 0
> > &&
> > +		    lcore_id != node->lcore_id && graph->rq != NULL &&
> > +		    __rte_graph_sched_node_enqueue(node, graph->rq))
> > +			goto next;
> > +
> >  		if (rte_graph_has_stats_feature()) {
> >  			start = rte_rdtsc();
> >  			rc = node->process(graph, node, objs, node->idx); @@ -215,6
> +225,7
> > @@ rte_graph_walk(struct rte_graph *graph)
> >  			node->process(graph, node, objs, node->idx);
> >  		}
> >  		node->idx = 0;
> > +	next:
> >  		head = likely((int32_t)head > 0) ? head & mask : head;
> >  	}
> >  	graph->tail = 0;
> > --
> > 2.25.1