[PATCH RFC v2 1/3] aio-poll: avoid unnecessary polling time computation

[Jaehoon Kim <jhkim@linux.ibm.com>]

Nodes are no longer added to poll_aio_handlers when adaptive polling is
disabled, preventing unnecessary try_poll_mode() calls. Additionally,
aio_poll() skips try_poll_mode() when timeout is 0.

This avoids iterating over all nodes to compute max_ns unnecessarily
when polling is disabled or timeout is 0.

Signed-off-by: Jaehoon Kim <jhkim@linux.ibm.com>
---
 util/aio-posix.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/util/aio-posix.c b/util/aio-posix.c
index 488d964611..b02beb0505 100644
--- a/util/aio-posix.c
+++ b/util/aio-posix.c
@@ -307,9 +307,8 @@ static bool aio_dispatch_handler(AioContext *ctx, AioHandler *node)
      * fdmon_supports_polling(), but only until the fd fires for the first
      * time.
      */
-    if (!QLIST_IS_INSERTED(node, node_deleted) &&
-        !QLIST_IS_INSERTED(node, node_poll) &&
-        node->io_poll) {
+    if (ctx->poll_max_ns && !QLIST_IS_INSERTED(node, node_deleted) &&
+        !QLIST_IS_INSERTED(node, node_poll) && node->io_poll) {
         trace_poll_add(ctx, node, node->pfd.fd, revents);
         if (ctx->poll_started && node->io_poll_begin) {
             node->io_poll_begin(node->opaque);
@@ -631,7 +630,7 @@ static void adjust_polling_time(AioContext *ctx, AioPolledEvent *poll,
 bool aio_poll(AioContext *ctx, bool blocking)
 {
     AioHandlerList ready_list = QLIST_HEAD_INITIALIZER(ready_list);
-    bool progress;
+    bool progress = false;
     bool use_notify_me;
     int64_t timeout;
     int64_t start = 0;
@@ -656,7 +655,9 @@ bool aio_poll(AioContext *ctx, bool blocking)
     }
 
     timeout = blocking ? aio_compute_timeout(ctx) : 0;
-    progress = try_poll_mode(ctx, &ready_list, &timeout);
+    if ((ctx->poll_max_ns != 0) && (timeout != 0)) {
+        progress = try_poll_mode(ctx, &ready_list, &timeout);
+    }
     assert(!(timeout && progress));
 
     /*
-- 
2.50.1