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gallium/util: don't let child processes inherit our thread affinity

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v2: corrected the comment
This commit is contained in:
Marek Olšák
2018-09-12 20:29:19 -04:00
parent 7d41a7593a
commit 914bd3014f
1 changed files with 32 additions and 4 deletions
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36
src/gallium/auxiliary/util/u_helpers.c
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@@ -121,17 +121,40 @@ util_upload_index_buffer(struct pipe_context *pipe,
return *out_buffer != NULL;
}
#ifdef HAVE_PTHREAD_SETAFFINITY
static unsigned L3_cache_number;
static once_flag init_cache_number_flag = ONCE_FLAG_INIT;
static once_flag thread_pinning_once_flag = ONCE_FLAG_INIT;
static void
util_init_cache_number(void)
util_set_full_cpu_affinity(void)
{
cpu_set_t cpuset;
CPU_ZERO(&cpuset);
for (unsigned i = 0; i < CPU_SETSIZE; i++)
CPU_SET(i, &cpuset);
pthread_setaffinity_np(pthread_self(), sizeof(cpuset), &cpuset);
}
static void
util_init_thread_pinning(void)
{
/* Get a semi-random number. */
int64_t t = os_time_get_nano();
L3_cache_number = (t ^ (t >> 8) ^ (t >> 16));
/* Reset thread affinity for all child processes to prevent them from
* inheriting the current thread's affinity.
*
* What happens if a driver is unloaded and the app creates a thread?
*/
pthread_atfork(NULL, NULL, util_set_full_cpu_affinity);
}
#endif
/**
* Called by MakeCurrent. Used to notify the driver that the application
* thread may have been changed.
@@ -146,18 +169,23 @@ util_init_cache_number(void)
void
util_context_thread_changed(struct pipe_context *ctx, thrd_t *upper_thread)
{
#ifdef HAVE_PTHREAD
#ifdef HAVE_PTHREAD_SETAFFINITY
/* If pinning has no effect, don't do anything. */
if (util_cpu_caps.nr_cpus == util_cpu_caps.cores_per_L3)
return;
thrd_t current = thrd_current();
int cache = util_get_L3_for_pinned_thread(current,
util_cpu_caps.cores_per_L3);
call_once(&thread_pinning_once_flag, util_init_thread_pinning);
/* If the main thread is not pinned, choose the L3 cache. */
if (cache == -1) {
unsigned num_L3_caches = util_cpu_caps.nr_cpus /
util_cpu_caps.cores_per_L3;
/* Choose a different L3 cache for each subsequent MakeCurrent. */
call_once(&init_cache_number_flag, util_init_cache_number);
cache = p_atomic_inc_return(&L3_cache_number) % num_L3_caches;
util_pin_thread_to_L3(current, cache, util_cpu_caps.cores_per_L3);
}