--- psort.c.orig 2008-11-24 17:01:07.000000000 -0800
+++ psort.c 2008-11-24 22:02:57.000000000 -0800
@@ -1,3 +1,4 @@
+/****************************************************************************/
/*-
* Copyright (c) 1992, 1993
* The Regents of the University of California. All rights reserved.
@@ -34,14 +35,22 @@ static char sccsid[] = "@(#)qsort.c 8.1
__FBSDID("$FreeBSD: src/lib/libc/stdlib/qsort.c,v 1.15 2008/01/14 09:21:34 das Exp $");
#include <stdlib.h>
+#include <pthread.h>
+#include <dispatch/dispatch.h>
+#include <stddef.h>
#include <string.h>
+#include <libkern/OSAtomic.h>
+#include <sys/mman.h>
+#include <errno.h>
+#define __APPLE_API_PRIVATE
+#include <machine/cpu_capabilities.h>
-#ifdef I_AM_QSORT_R
+#ifdef I_AM_PSORT_R
typedef int cmp_t(void *, const void *, const void *);
#else
typedef int cmp_t(const void *, const void *);
#endif
-#ifdef I_AM_QSORT_B
+#ifdef I_AM_PSORT_B
static inline char *med3(char *, char *, char *, cmp_t ^, void *) __attribute__((always_inline));
#else
static inline char *med3(char *, char *, char *, cmp_t *, void *) __attribute__((always_inline));
@@ -50,6 +59,83 @@ static inline void swapfunc(char *, cha
#define min(a, b) (a) < (b) ? a : b
+#define NARGS ((PAGESIZE - offsetof(struct page, args)) / sizeof(union args))
+#define PAGESIZE 4096
+#define PARALLEL_MIN_SIZE 2000 /* determine heuristically */
+
+struct shared; /* forward reference */
+union args {
+ union args *next;
+ struct {
+ struct shared *shared;
+ void *a;
+ size_t n;
+ int depth_limit;
+ } /* anonymous */;
+};
+
+struct page {
+ struct page *next;
+ union args args[0];
+};
+
+struct shared {
+ char *who;
+ union args *freelist;
+ struct page *pagelist;
+#ifdef I_AM_PSORT_R
+ void *thunk;
+#endif
+#ifdef I_AM_PSORT_B
+ cmp_t ^cmp;
+#else
+ cmp_t *cmp;
+#endif
+ size_t es;
+ size_t turnoff;
+ dispatch_queue_t queue;
+ pthread_cond_t cond;
+ pthread_mutex_t mutex;
+ OSSpinLock sharedlock;
+ int count;
+};
+
+static union args *
+getargs(struct shared *shared)
+{
+ union args *args;
+
+ OSSpinLockLock(&shared->sharedlock);
+ if(!shared->freelist) {
+ struct page *page;
+ union args *prev;
+ int i;
+ if((page = (struct page *)mmap(NULL, PAGESIZE, PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, -1, 0)) == NULL)
+ return NULL;
+ page->next = shared->pagelist;
+ shared->pagelist = page;
+ prev = NULL;
+ for(args = page->args, i = NARGS; i > 0; args++, i--) {
+ args->next = prev;
+ prev = args;
+ }
+ shared->freelist = prev;
+ }
+ args = shared->freelist;
+ shared->freelist = args->next;
+ OSSpinLockUnlock(&shared->sharedlock);
+ return args;
+}
+
+static void
+returnargs(struct shared *shared, union args *args)
+{
+ OSSpinLockLock(&shared->sharedlock);
+ args->next = shared->freelist;
+ shared->freelist = args;
+ OSSpinLockUnlock(&shared->sharedlock);
+}
+
/*
* Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
*/
@@ -88,7 +174,7 @@ swapfunc(a, b, n, swaptype)
#define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype)
-#ifdef I_AM_QSORT_R
+#ifdef I_AM_PSORT_R
#define CMP(t, x, y) (cmp((t), (x), (y)))
#else
#define CMP(t, x, y) (cmp((x), (y)))
@@ -96,13 +182,13 @@ swapfunc(a, b, n, swaptype)
static inline char *
med3(char *a, char *b, char *c,
-#ifdef I_AM_QSORT_B
+#ifdef I_AM_PSORT_B
cmp_t ^cmp,
#else
cmp_t *cmp,
#endif
void *thunk
-#ifndef I_AM_QSORT_R
+#ifndef I_AM_PSORT_R
__unused
#endif
)
@@ -118,23 +204,25 @@ __unused
#define DEPTH(x) (2 * (fls((int)(x)) - 1))
#endif /* __LP64__ */
-#ifdef I_AM_QSORT_R
+#ifdef I_AM_PSORT_R
int __heapsort_r(void *, size_t, size_t, void *, int (*)(void *, const void *, const void *));
#endif
+static void _psort_parallel(void *x);
+
static void
-_qsort(void *a, size_t n, size_t es,
-#ifdef I_AM_QSORT_R
+_psort(void *a, size_t n, size_t es,
+#ifdef I_AM_PSORT_R
void *thunk,
#else
#define thunk NULL
#endif
-#ifdef I_AM_QSORT_B
+#ifdef I_AM_PSORT_B
cmp_t ^cmp,
#else
cmp_t *cmp,
#endif
-int depth_limit)
+int depth_limit, struct shared *shared)
{
char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
size_t d, r;
@@ -143,9 +231,9 @@ int depth_limit)
loop:
if (depth_limit-- <= 0) {
-#ifdef I_AM_QSORT_B
+#ifdef I_AM_PSORT_B
heapsort_b(a, n, es, cmp);
-#elif defined(I_AM_QSORT_R)
+#elif defined(I_AM_PSORT_R)
__heapsort_r(a, n, es, thunk, cmp);
#else
heapsort(a, n, es, cmp);
@@ -222,33 +310,135 @@ loop:
}
nevermind:
- if ((r = pb - pa) > es)
-#ifdef I_AM_QSORT_R
- _qsort(a, r / es, es, thunk, cmp, depth_limit);
+ if ((r = pb - pa) > es) {
+ r /= es;
+ if (shared && r > shared->turnoff) {
+ union args *args = getargs(shared);
+
+ if (args == NULL)
+ LIBC_ABORT("%s: getargs: %s", shared->who, strerror(errno));
+ args->shared = shared;
+ args->a = a;
+ args->n = r;
+ args->depth_limit = depth_limit;
+ OSAtomicIncrement32(&shared->count);
+ dispatch_async_f(shared->queue, args, _psort_parallel);
+ } else {
+#ifdef I_AM_PSORT_R
+ _psort(a, r, es, thunk, cmp, depth_limit, NULL);
#else
- _qsort(a, r / es, es, cmp, depth_limit);
+ _psort(a, r, es, cmp, depth_limit, NULL);
#endif
+ }
+ }
if ((r = pd - pc) > es) {
/* Iterate rather than recurse to save stack space */
a = pn - r;
n = r / es;
goto loop;
}
-/* qsort(pn - r, r / es, es, cmp);*/
+/* psort(pn - r, r / es, es, cmp);*/
+}
+
+static void
+_psort_parallel(void *x)
+{
+ union args *args = (union args *)x;
+ struct shared *shared = args->shared;
+
+ _psort(args->a, args->n, shared->es,
+#ifdef I_AM_PSORT_R
+ shared->thunk,
+#endif
+ shared->cmp, args->depth_limit, shared);
+ returnargs(shared, args);
+ if(OSAtomicDecrement32(&shared->count) <= 0) {
+ pthread_mutex_lock(&shared->mutex);
+ pthread_cond_signal(&shared->cond);
+ pthread_mutex_unlock(&shared->mutex);
+ }
+}
+
+/* fast, approximate integer square root */
+static size_t
+isqrt(size_t x)
+{
+ size_t s = 1L << (flsl(x) / 2);
+ return (s + x / s) / 2;
}
void
-#ifdef I_AM_QSORT_R
-qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
-#elif defined(I_AM_QSORT_B)
-qsort_b(void *a, size_t n, size_t es, cmp_t ^cmp)
+#ifdef I_AM_PSORT_R
+psort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
+#elif defined(I_AM_PSORT_B)
+psort_b(void *a, size_t n, size_t es, cmp_t ^cmp)
#else
-qsort(void *a, size_t n, size_t es, cmp_t *cmp)
+psort(void *a, size_t n, size_t es, cmp_t *cmp)
#endif
{
- _qsort(a, n, es,
-#ifdef I_AM_QSORT_R
- thunk,
+ if (n >= PARALLEL_MIN_SIZE && _NumCPUs() > 1) {
+ struct shared shared;
+ union args *args;
+
+ bzero(&shared, sizeof(shared));
+ shared.sharedlock = OS_SPINLOCK_INIT;
+ if ((args = getargs(&shared)) != NULL) {
+ struct page *p, *pp;
+#ifdef I_AM_PSORT_R
+ shared.who = "psort_r";
+ shared.thunk = thunk;
+#elif defined(I_AM_PSORT_B)
+ shared.who = "psort_b";
+#else
+ shared.who = "psort";
+#endif
+ shared.cmp = cmp;
+ shared.es = es;
+ shared.queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
+ shared.cond = (pthread_cond_t)PTHREAD_COND_INITIALIZER;
+ shared.mutex = (pthread_mutex_t)PTHREAD_MUTEX_INITIALIZER;
+ args->a = a;
+ args->n = n;
+ args->depth_limit = DEPTH(n);
+ args->shared = &shared;
+ /*
+ * The turnoff value is the size of a partition that,
+ * below which, we stop doing in parallel, and just do
+ * in the current thread. The value of sqrt(n) was
+ * determined heuristically. There is a smaller
+ * dependence on the slowness of the comparison
+ * function, and there might be a dependence on the
+ * number of processors, but the algorithm has not been
+ * determined. Because the sensitivity to the turnoff
+ * value is relatively low, we use a fast, approximate
+ * integer square root routine that is good enough for
+ * this purpose.
+ */
+ shared.turnoff = isqrt(n);
+ OSAtomicIncrement32(&shared.count);
+ _psort_parallel(args);
+
+ /* wait for queue to drain */
+ pthread_mutex_lock(&shared.mutex);
+ while(shared.count > 0)
+ pthread_cond_wait(&shared.cond, &shared.mutex);
+
+ pthread_mutex_unlock(&shared.mutex);
+ pthread_mutex_destroy(&shared.mutex);
+ pthread_cond_destroy(&shared.cond);
+ for(p = shared.pagelist; p; p = pp) {
+ pp = p->next;
+ munmap(p, PAGESIZE);
+ }
+ return;
+ }
+ }
+ /* Just call qsort */
+#ifdef I_AM_PSORT_R
+ qsort_r(a, n, es, thunk, cmp);
+#elif defined(I_AM_PSORT_B)
+ qsort_b(a, n, es, cmp);
+#else
+ qsort(a, n, es, cmp);
#endif
- cmp, DEPTH(n));
}