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From: "Pedro F. Giffuni" <pfg@FreeBSD.org>
Date: Mon, 6 Feb 2017 05:27:05 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
svn-src-stable@freebsd.org, svn-src-stable-10@freebsd.org
Subject: svn commit: r313321 - stable/10/usr.bin/sort
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X-List-Received-Date: Mon, 06 Feb 2017 05:27:06 -0000
Author: pfg
Date: Mon Feb 6 05:27:05 2017
New Revision: 313321
URL: https://svnweb.freebsd.org/changeset/base/313321
Log:
MFC r312667:
sort - Don't live-loop threads.
Worker threads now use a pthread_cond_t to wait for work instead of
burning the cpu up.
Obtained from: DragonflyBSD (07774aea0ccf64a48fcfad8899e3bf7c8f18277a)
Modified:
stable/10/usr.bin/sort/radixsort.c
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/usr.bin/sort/radixsort.c
==============================================================================
--- stable/10/usr.bin/sort/radixsort.c Mon Feb 6 05:24:17 2017 (r313320)
+++ stable/10/usr.bin/sort/radixsort.c Mon Feb 6 05:27:05 2017 (r313321)
@@ -83,12 +83,12 @@ static struct level_stack *g_ls;
#if defined(SORT_THREADS)
/* stack guarding mutex */
+static pthread_cond_t g_ls_cond;
static pthread_mutex_t g_ls_mutex;
/* counter: how many items are left */
static size_t sort_left;
/* guarding mutex */
-static pthread_mutex_t sort_left_mutex;
/* semaphore to count threads */
static sem_t mtsem;
@@ -99,23 +99,25 @@ static sem_t mtsem;
static inline void
sort_left_dec(size_t n)
{
-
- pthread_mutex_lock(&sort_left_mutex);
+ pthread_mutex_lock(&g_ls_mutex);
sort_left -= n;
- pthread_mutex_unlock(&sort_left_mutex);
+ if (sort_left == 0 && nthreads > 1)
+ pthread_cond_broadcast(&g_ls_cond);
+ pthread_mutex_unlock(&g_ls_mutex);
}
/*
* Do we have something to sort ?
+ *
+ * This routine does not need to be locked.
*/
static inline bool
have_sort_left(void)
{
bool ret;
- pthread_mutex_lock(&sort_left_mutex);
ret = (sort_left > 0);
- pthread_mutex_unlock(&sort_left_mutex);
+
return (ret);
}
@@ -146,6 +148,11 @@ push_ls(struct sort_level* sl)
#if defined(SORT_THREADS)
if (nthreads > 1)
+ pthread_cond_signal(&g_ls_cond);
+#endif
+
+#if defined(SORT_THREADS)
+ if (nthreads > 1)
pthread_mutex_unlock(&g_ls_mutex);
#endif
}
@@ -184,13 +191,19 @@ pop_ls_mt(void)
pthread_mutex_lock(&g_ls_mutex);
- if (g_ls) {
- sl = g_ls->sl;
- saved_ls = g_ls;
- g_ls = g_ls->next;
- } else {
+ for (;;) {
+ if (g_ls) {
+ sl = g_ls->sl;
+ saved_ls = g_ls;
+ g_ls = g_ls->next;
+ break;
+ }
sl = NULL;
saved_ls = NULL;
+
+ if (have_sort_left() == 0)
+ break;
+ pthread_cond_wait(&g_ls_cond, &g_ls_mutex);
}
pthread_mutex_unlock(&g_ls_mutex);
@@ -493,13 +506,8 @@ run_sort_cycle_mt(void)
for (;;) {
slc = pop_ls_mt();
- if (slc == NULL) {
- if (have_sort_left()) {
- pthread_yield();
- continue;
- }
+ if (slc == NULL)
break;
- }
run_sort_level_next(slc);
}
}
@@ -510,9 +518,7 @@ run_sort_cycle_mt(void)
static void*
sort_thread(void* arg)
{
-
run_sort_cycle_mt();
-
sem_post(&mtsem);
return (arg);
@@ -608,8 +614,7 @@ run_top_sort_level(struct sort_level *sl
pthread_t pth;
pthread_attr_init(&attr);
- pthread_attr_setdetachstate(&attr,
- PTHREAD_DETACHED);
+ pthread_attr_setdetachstate(&attr, PTHREAD_DETACHED);
for (;;) {
int res = pthread_create(&pth, &attr,
@@ -626,7 +631,7 @@ run_top_sort_level(struct sort_level *sl
pthread_attr_destroy(&attr);
}
- for(i = 0; i < nthreads; ++i)
+ for (i = 0; i < nthreads; ++i)
sem_wait(&mtsem);
}
#endif /* defined(SORT_THREADS) */
@@ -649,7 +654,7 @@ run_sort(struct sort_list_item **base, s
pthread_mutexattr_settype(&mattr, PTHREAD_MUTEX_ADAPTIVE_NP);
pthread_mutex_init(&g_ls_mutex, &mattr);
- pthread_mutex_init(&sort_left_mutex, &mattr);
+ pthread_cond_init(&g_ls_cond, NULL);
pthread_mutexattr_destroy(&mattr);
@@ -677,7 +682,6 @@ run_sort(struct sort_list_item **base, s
if (nthreads > 1) {
sem_destroy(&mtsem);
pthread_mutex_destroy(&g_ls_mutex);
- pthread_mutex_destroy(&sort_left_mutex);
}
nthreads = nthreads_save;
#endif