From 93b21d2d944b375abeb61aca517fd2279b7b30d6 Mon Sep 17 00:00:00 2001 From: Con Kolivas Date: Wed, 6 May 2020 18:03:37 +1000 Subject: [PATCH] Linux: Change minimum priority threads from SCHED_IDLE to nice 19 SCHED_BATCH. SCHED_IDLE on linux can lead to extraordinarily long periods of no scheduling leading to starvation of minimum priority threads for such an extended period that it can eventually lead to GUI stalls. Switch to renicing the threads to the lowest priority and use the SCHED_BATCH scheduling policy which is a hint to the scheduler that this is latency insensitive thread instead. This change has been confirmed to address unexpected GUI related stalls in mesa applications across a range of different linux kernels. Signed-off-by: Con Kolivas --- src/util/u_queue.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/src/util/u_queue.c b/src/util/u_queue.c index 4049a4c7692..1598403b428 100644 --- a/src/util/u_queue.c +++ b/src/util/u_queue.c @@ -33,6 +33,12 @@ #include "util/u_thread.h" #include "u_process.h" +#if defined(__linux__) +#include +#include +#endif + + /* Define 256MB */ #define S_256MB (256 * 1024 * 1024) @@ -258,6 +264,15 @@ util_queue_thread_func(void *input) } #endif +#if defined(__linux__) + if (queue->flags & UTIL_QUEUE_INIT_USE_MINIMUM_PRIORITY) { + pid_t tid = gettid(); + + /* The nice() function can only set a maximum of 19. */ + setpriority(PRIO_PROCESS, tid, 19); + } +#endif + if (strlen(queue->name) > 0) { char name[16]; snprintf(name, sizeof(name), "%s%i", queue->name, thread_index); @@ -331,16 +346,17 @@ util_queue_create_thread(struct util_queue *queue, unsigned index) } if (queue->flags & UTIL_QUEUE_INIT_USE_MINIMUM_PRIORITY) { -#if defined(__linux__) && defined(SCHED_IDLE) +#if defined(__linux__) && defined(SCHED_BATCH) struct sched_param sched_param = {0}; /* The nice() function can only set a maximum of 19. - * SCHED_IDLE is the same as nice = 20. + * SCHED_BATCH gives the scheduler a hint that this is a latency + * insensitive thread. * * Note that Linux only allows decreasing the priority. The original * priority can't be restored. */ - pthread_setschedparam(queue->threads[index], SCHED_IDLE, &sched_param); + pthread_setschedparam(queue->threads[index], SCHED_BATCH, &sched_param); #endif } return true; -- 2.25.1