MINOR: task: make rqueue_ticks atomic

The runqueue ticks counter is per-thread and wasn't initially meant to
be shared. We'll soon have to share it so let's make it atomic. It's
only updated when waking up a task, and no performance difference was
observed. It was moved in the thread_ctx struct so that it doesn't
pollute the local cache line when it's later updated by other threads.

diff --git a/include/haproxy/tinfo-t.h b/include/haproxy/tinfo-t.h
index b2395a4d5f3ca190416d4bc40309f9fdb969a160..df5ac7ab32e8fabe1eb75fbb3c71a036d1ab312c 100644 (file)
--- a/include/haproxy/tinfo-t.h
+++ b/include/haproxy/tinfo-t.h
@@ -79,7 +79,6 @@ struct thread_ctx {
        struct eb_root timers;              /* tree constituting the per-thread wait queue */
        struct eb_root rqueue;              /* tree constituting the per-thread run queue */
        struct task *current;               /* current task (not tasklet) */
-       unsigned int rqueue_ticks;          /* Insertion counter for the run queue */
        int current_queue;                  /* points to current tasklet list being run, -1 if none */
        unsigned int nb_tasks;              /* number of tasks allocated on this thread */
        uint flags;                         /* thread flags, TH_FL_* */
@@ -96,11 +95,13 @@ struct thread_ctx {
        // third cache line here on 64 bits: accessed mostly using atomic ops
        ALWAYS_ALIGN(64);
        struct mt_list shared_tasklet_list; /* Tasklet to be run, woken up by other threads */
+       unsigned int rqueue_ticks;          /* Insertion counter for the run queue */
        unsigned int rq_total;              /* total size of the run queue, prio_tree + tasklets */
        int tasks_in_list;                  /* Number of tasks in the per-thread tasklets list */
+       uint idle_pct;                      /* idle to total ratio over last sample (percent) */
+
        uint64_t prev_cpu_time;             /* previous per thread CPU time */
        uint64_t prev_mono_time;            /* previous system wide monotonic time  */
-       uint idle_pct;                      /* idle to total ratio over last sample (percent) */
        ALWAYS_ALIGN(128);
 };
 

diff --git a/src/task.c b/src/task.c
index b371b89a9cc96fd7a7bca4471f6e44d3d5977b11..247ed807a0a86bbff91af9604d115056b984c0d4 100644 (file)
--- a/src/task.c
+++ b/src/task.c
@@ -249,7 +249,7 @@ void __task_wakeup(struct task *t)
 #endif
        {
                _HA_ATOMIC_INC(&th_ctx->rq_total);
-               t->rq.key = ++th_ctx->rqueue_ticks;
+               t->rq.key = _HA_ATOMIC_ADD_FETCH(&th_ctx->rqueue_ticks, 1);
        }
 
        if (likely(t->nice)) {
@@ -854,7 +854,7 @@ void process_runnable_tasks()
                 */
 
                if (!lrq) {
-                       lrq = eb32sc_lookup_ge(&tt->rqueue, tt->rqueue_ticks - TIMER_LOOK_BACK, tid_bit);
+                       lrq = eb32sc_lookup_ge(&tt->rqueue, _HA_ATOMIC_LOAD(&tt->rqueue_ticks) - TIMER_LOOK_BACK, tid_bit);
                        if (unlikely(!lrq))
                                lrq = eb32sc_first(&tt->rqueue, tid_bit);
                }