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event: replace poller rte_ring with TAILQ

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The rte_ring used for pollers is already single-producer and
single-consumer, so it is not providing any thread safety guarantees.
ALl modifications to the active_pollers ring are done from the core that
is running the reactor (via events).  This means the rte_ring can be
replaced with a simpler intrusive linked list.

This simplifies the removal of pollers in the middle of the list and
avoids extra allocations for the ring.

Change-Id: Ica149b7a1668a8af1e6ca8f741c48f2217f6f9bf
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>
This commit is contained in:
Daniel Verkamp 2016-07-28 08:50:50 -07:00
parent bd4ac74eaf
commit 921bf34289
2 changed files with 13 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
include/spdk/event.h
View File

@ -103,19 +103,12 @@ typedef void (*spdk_poller_fn)(void *arg);
* \brief A poller is a function that is repeatedly called on an lcore.
*/
struct spdk_poller {
uint32_t lcore;
spdk_poller_fn fn;
void *arg;
TAILQ_ENTRY(spdk_poller) tailq;
uint32_t lcore;
spdk_poller_fn fn;
void *arg;
};
#define SPDK_POLLER_RING_SIZE 4096
/*
* -1 accounts for the empty slot needed to differentiate between ring empty
* and ring full.
*/
#define SPDK_MAX_POLLERS_PER_CORE (SPDK_POLLER_RING_SIZE - 1)
typedef void (*spdk_app_shutdown_cb)(void);
typedef void (*spdk_sighandler_t)(int);

39
lib/event/reactor.c
View File

@ -76,7 +76,7 @@ struct spdk_reactor {
* of the ring, executes it, then puts it back at the tail of
* the ring.
*/
struct rte_ring *active_pollers;
TAILQ_HEAD(, spdk_poller) active_pollers;
struct rte_ring *events;
};
@ -253,8 +253,7 @@ static int
_spdk_reactor_run(void *arg)
{
struct spdk_reactor *reactor = arg;
struct spdk_poller *poller = NULL;
int rc;
struct spdk_poller *poller;
set_reactor_thread_name();
SPDK_NOTICELOG("waiting for work item to arrive...\n");
@ -264,14 +263,11 @@ _spdk_reactor_run(void *arg)
rte_timer_manage();
if (rte_ring_dequeue(reactor->active_pollers, (void **)&poller) == 0) {
poller = TAILQ_FIRST(&reactor->active_pollers);
if (poller) {
TAILQ_REMOVE(&reactor->active_pollers, poller, tailq);
poller->fn(poller->arg);
rc = rte_ring_enqueue(reactor->active_pollers,
(void *)poller);
if (rc != 0) {
SPDK_ERRLOG("poller could not be enqueued\n");
exit(EXIT_FAILURE);
}
TAILQ_INSERT_TAIL(&reactor->active_pollers, poller, tailq);
}
if (g_reactor_state != SPDK_REACTOR_STATE_RUNNING) {
@ -289,10 +285,7 @@ spdk_reactor_construct(struct spdk_reactor *reactor, uint32_t lcore)
reactor->lcore = lcore;
snprintf(ring_name, sizeof(ring_name), "spdk_active_pollers_%d", lcore);
reactor->active_pollers =
rte_ring_create(ring_name, SPDK_POLLER_RING_SIZE, rte_lcore_to_socket_id(lcore),
RING_F_SP_ENQ | RING_F_SC_DEQ);
TAILQ_INIT(&reactor->active_pollers);
snprintf(ring_name, sizeof(ring_name) - 1, "spdk_event_queue_%u", lcore);
reactor->events =
@ -530,7 +523,7 @@ _spdk_event_add_poller(spdk_event_t event)
poller->lcore = reactor->lcore;
rte_ring_enqueue(reactor->active_pollers, (void *)poller);
TAILQ_INSERT_TAIL(&reactor->active_pollers, poller, tailq);
if (next) {
spdk_event_call(next);
@ -555,22 +548,8 @@ _spdk_event_remove_poller(spdk_event_t event)
struct spdk_reactor *reactor = spdk_event_get_arg1(event);
struct spdk_poller *poller = spdk_event_get_arg2(event);
struct spdk_event *next = spdk_event_get_next(event);
struct spdk_poller *tmp = NULL;
uint32_t i;
int rc;
/* Loop over all pollers, without breaking early, so that
* the list of pollers stays in the same order. */
for (i = 0; i < rte_ring_count(reactor->active_pollers); i++) {
rte_ring_dequeue(reactor->active_pollers, (void **)&tmp);
if (tmp != poller) {
rc = rte_ring_enqueue(reactor->active_pollers, (void *)tmp);
if (rc != 0) {
SPDK_ERRLOG("poller could not be enqueued\n");
exit(EXIT_FAILURE);
}
}
}
TAILQ_REMOVE(&reactor->active_pollers, poller, tailq);
if (next) {
spdk_event_call(next);