* Written by Josh Dybnis and released to the public domain, as explained at
* http://creativecommons.org/licenses/publicdomain
*
- * safe memory reclemation using a simple technique from rcu
+ * safe memory reclamation using a simple technique from rcu
+ *
+ * WARNING: not robust enough for real-world use
*/
#include <string.h>
#include "common.h"
-#include "runtime_local.h"
+#include "rlocal.h"
#include "lwt.h"
#include "mem.h"
#include "tls.h"
void *x[0];
} fifo_t;
+#define MOD_SCALE(x, b) ((x) & MASK(b))
static uint64_t rcu_[MAX_NUM_THREADS][MAX_NUM_THREADS] = {};
static uint64_t rcu_last_posted_[MAX_NUM_THREADS][MAX_NUM_THREADS] = {};
static fifo_t *pending_[MAX_NUM_THREADS] = {};
return q;
}
-static uint32_t fifo_index (fifo_t *q, uint32_t i) {
- return i & MASK(q->scale);
-}
-
-static void fifo_enqueue (fifo_t *q, void *x) {
- assert(fifo_index(q, q->head + 1) != fifo_index(q, q->tail));
- uint32_t i = fifo_index(q, q->head++);
- q->x[i] = x;
-}
-
-static void *fifo_dequeue (fifo_t *q) {
- uint32_t i = fifo_index(q, q->tail++);
- return q->x[i];
-}
-
void rcu_thread_init (int id) {
assert(id < MAX_NUM_THREADS);
if (pending_[id] == NULL) {
}
}
-static void rcu_post (uint64_t x) {
- LOCALIZE_THREAD_LOCAL(tid_, int);
- if (x - rcu_last_posted_[tid_][tid_] < RCU_POST_THRESHOLD)
- return;
-
- int next_thread_id = (tid_ + 1) % num_threads_;
-
- TRACE("r0", "rcu_post: %llu", x, 0);
- rcu_[next_thread_id][tid_] = rcu_last_posted_[tid_][tid_] = x;
-}
-
void rcu_update (void) {
LOCALIZE_THREAD_LOCAL(tid_, int);
assert(tid_ < num_threads_);
// free
while (pending_[tid_]->tail != rcu_[tid_][tid_]) {
- nbd_free(fifo_dequeue(pending_[tid_]));
+ fifo_t *q = pending_[tid_];
+ uint32_t i = MOD_SCALE(q->tail++, q->scale);
+ nbd_free(q->x[i]);
}
}
void nbd_defer_free (void *x) {
LOCALIZE_THREAD_LOCAL(tid_, int);
- fifo_enqueue(pending_[tid_], x);
+ fifo_t *q = pending_[tid_];
+ assert(MOD_SCALE(q->head + 1, q->scale) != MOD_SCALE(q->tail, q->scale));
+ uint32_t i = MOD_SCALE(q->head++, q->scale);
+ q->x[i] = x;
TRACE("r0", "nbd_defer_free: put %p on queue at position %llu", x, pending_[tid_]->head);
- rcu_post(pending_[tid_]->head);
-}
-
-#ifdef MAKE_rcu_test
-#include <errno.h>
-#include <stdio.h>
-#include "runtime.h"
-
-#define NUM_ITERATIONS 10000000
-
-typedef struct node {
- struct node *next;
-} node_t;
-
-typedef struct lifo {
- node_t *head;
-} lifo_t;
-
-static volatile int wait_;
-static lifo_t *stk_;
-
-static lifo_t *lifo_alloc (void) {
- lifo_t *stk = (lifo_t *)nbd_malloc(sizeof(lifo_t));
- memset(stk, 0, sizeof(lifo_t));
- return stk;
-}
-
-static void lifo_aba_push (lifo_t *stk, node_t *x) {
- node_t *head;
- do {
- head = ((volatile lifo_t *)stk)->head;
- ((volatile node_t *)x)->next = head;
- } while (__sync_val_compare_and_swap(&stk->head, head, x) != head);
-}
-
-node_t *lifo_aba_pop (lifo_t *stk) {
- node_t *head;
- do {
- head = ((volatile lifo_t *)stk)->head;
- if (head == NULL)
- return NULL;
- } while (__sync_val_compare_and_swap(&stk->head, head, head->next) != head);
- head->next = NULL;
- return head;
-}
-
-node_t *node_alloc (void) {
- node_t *node = (node_t *)nbd_malloc(sizeof(node_t));
- memset(node, 0, sizeof(node_t));
- return node;
-}
-
-void *worker (void *arg) {
- int id = (int)(size_t)arg;
- unsigned int rand_seed = (unsigned int)id + 1;
-
- // Wait for all the worker threads to be ready.
- __sync_fetch_and_add(&wait_, -1);
- do {} while (wait_);
-
- int i;
- for (i = 0; i < NUM_ITERATIONS; ++ i) {
- int n = rand_r(&rand_seed);
- if (n & 0x1) {
- lifo_aba_push(stk_, node_alloc());
- } else {
- node_t *x = lifo_aba_pop(stk_);
- if (x) {
- nbd_defer_free(x);
- }
- }
- rcu_update();
- }
- return NULL;
-}
-
-int main (int argc, char **argv) {
- nbd_init();
- //lwt_set_trace_level("m0r0");
-
- int num_threads = 2;
- if (argc == 2)
- {
- errno = 0;
- num_threads = strtol(argv[1], NULL, 10);
- if (errno) {
- fprintf(stderr, "%s: Invalid argument for number of threads\n", argv[0]);
- return -1;
- }
- if (num_threads <= 0) {
- fprintf(stderr, "%s: Number of threads must be at least 1\n", argv[0]);
- return -1;
- }
- }
-
- stk_ = lifo_alloc();
- wait_ = num_threads;
-
- pthread_t thread[num_threads];
- for (int i = 0; i < num_threads; ++i) {
- int rc = nbd_thread_create(thread + i, i, worker, (void *)(size_t)i);
- if (rc != 0) { perror("pthread_create"); return rc; }
- }
- for (int i = 0; i < num_threads; ++i) {
- pthread_join(thread[i], NULL);
- }
-
- return 0;
+ if (pending_[tid_]->head - rcu_last_posted_[tid_][tid_] < RCU_POST_THRESHOLD)
+ return;
+ TRACE("r0", "nbd_defer_free: posting %llu", pending_[tid_]->head, 0);
+ int next_thread_id = (tid_ + 1) % num_threads_;
+ rcu_[next_thread_id][tid_] = rcu_last_posted_[tid_][tid_] = pending_[tid_]->head;
}
-#endif//rcu_test
projects / nbds / blobdiff