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MINOR: task: make rqueue_ticks atomic

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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.
This commit is contained in:
Willy Tarreau 2022-06-16 15:44:35 +02:00
parent fc5de15baa
commit a4fb79b4a2
2 changed files with 5 additions and 4 deletions
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5
include/haproxy/tinfo-t.h
View File

@ -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);
};

4
src/task.c
View File

@ -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);
}