ms-queue: cleanups, convert to C11 atomics
authorBrian Norris <banorris@uci.edu>
Wed, 6 Mar 2013 00:29:51 +0000 (16:29 -0800)
committerBrian Norris <banorris@uci.edu>
Wed, 6 Mar 2013 00:29:51 +0000 (16:29 -0800)
This converts the "pointer" to a 64-bit type (unsigned long long, or
'pointer') divided into two 32-bit halves (ptr and count), instead of
using a union of a struct and an 'unsigned long'.

All atomics are seq_cst for now. Once the code all looks a little
better, I'll relax these to reasonable memory orderings.

ms-queue/args.c
ms-queue/main.c
ms-queue/my_queue.c
ms-queue/my_queue.h

index 89101e5..6fe19de 100644 (file)
@@ -1,25 +1,17 @@
 #include "main.h"
 
 extern unsigned iterations;
-extern unsigned multi;
-extern unsigned initial_nodes;
 extern unsigned procs;
-extern unsigned repetitions;
-extern unsigned work;
 
 void parse_args(int argc, char **argv)
 {
-       extern char * optarg;
+       extern char *optarg;
        int c;
 
-       while ((c = getopt(argc, argv, "i:m:n:p:r:w:")) != EOF)
+       while ((c = getopt(argc, argv, "i:p:")) != EOF)
                switch(c) {
                        case 'i':  iterations = atoi(optarg); break;
-                       case 'm':  multi = atoi(optarg);  break;
-                       case 'n':  initial_nodes = atoi(optarg);  break;
                        case 'p':   procs = atoi(optarg);   break;
-                       case 'r':   repetitions = atoi(optarg);   break;
-                       case 'w':   work = atoi(optarg);   break;
                        default:
                                    assert(0);
                }
index 015fbd4..30d9da9 100644 (file)
@@ -1,78 +1,52 @@
 #include "main.h"
 #include <stdlib.h>
 
-#define NUM_PROCESSORS                 12
-
-struct tms tim;
-struct tms tim1;
-
-int shmid;
-
-unsigned pid;
-char* name = "";
-unsigned procs = 1;
-unsigned multi = 1;
+unsigned procs = 2;
 unsigned iterations = 1;
-unsigned initial_nodes = 0;
-unsigned repetitions = 1;
-unsigned work = 0;
 private_t private;
 shared_mem_t *smp;
 
-void time_test()
+static void main_task(void *param)
 {
-       unsigned i,j;
-       struct tms time_val;
-       clock_t t1, t2;
+       unsigned i, j;
        unsigned val;
+       int pid = *((int *)param);
 
-       if(pid==0) {
-               init_queue();
-       }
        init_memory();
-       init_private();
-       for(i=0;i<iterations;i++) {
+       init_private(pid);
+       for (i = 0; i < iterations; i++) {
                val = private.value;
                enqueue(val);
-               for(j=0; j<work;) j++;
                val = dequeue();
-               for(j=0; j<work;) j++;
                private.value++;
        }
 }
 
-void main_task()
-{
-       unsigned processor;
-       unsigned i;
-
-       processor = (pid/multi)+1;
-       processor %= NUM_PROCESSORS;
-       for (i=0; i<repetitions; i++) {
-               time_test();
-       }
-}
-
 int user_main(int argc, char **argv)
 {
        int i, num_threads;
        thrd_t *t;
+       int *param;
 
        parse_args(argc, argv);
-       name = argv[0];
-       iterations = (iterations + ((procs*multi)>>1))/(procs*multi);
+       iterations = (iterations + (procs >> 1)) / procs;
 
        smp = (shared_mem_t *)calloc(1, sizeof(shared_mem_t));
        assert(smp);
 
-       num_threads = procs * multi;
+       num_threads = procs;
        t = malloc(num_threads * sizeof(thrd_t));
+       param = malloc(num_threads * sizeof(*param));
 
-       for (i = 0; i < num_threads; i++)
-               thrd_create(&t[i], main_task, NULL);
+       init_queue();
+       for (i = 0; i < num_threads; i++) {
+               param[i] = i;
+               thrd_create(&t[i], main_task, &param[i]);
+       }
        for (i = 0; i < num_threads; i++)
                thrd_join(t[i]);
 
+       free(param);
        free(t);
        free(smp);
 
index 1f8a446..8fedd9c 100644 (file)
@@ -1,15 +1,13 @@
 #include "main.h"
 
-extern unsigned pid;
-extern unsigned iterations;
-extern unsigned initial_nodes;
+extern unsigned int iterations;
 extern private_t private;
-extern shared_mem_tsmp;
+extern shared_mem_t *smp;
 
-void init_private()
+void init_private(int pid)
 {
-       private.node = 2 + initial_nodes + pid;
-       private.value = 1 + initial_nodes + (pid * iterations);
+       private.node = 2 + pid;
+       private.value = 1 + (pid * iterations);
 
 }
 
@@ -17,114 +15,116 @@ void init_memory()
 {
 }
 
-static unsigned new_node()
+static unsigned int new_node()
 {
        return private.node;
 }
 
-static void reclaim(unsigned node)
+static void reclaim(unsigned int node)
 {
        private.node = node;
 }
 
 void init_queue()
 {
-       unsigned i;
+       unsigned int i;
+       pointer head;
+       pointer tail;
+       pointer next;
 
        /* initialize queue */
-       smp->head.sep.ptr = 1;
-       smp->head.sep.count = 0;
-       smp->tail.sep.ptr = 1;
-       smp->tail.sep.count = 0;
-       smp->nodes[1].next.sep.ptr = NULL;
-       smp->nodes[1].next.sep.count = 0;
+       head = MAKE_POINTER(1, 0);
+       tail = MAKE_POINTER(1, 0);
+       next = MAKE_POINTER(0, 0); // (NULL, 0)
+
+       atomic_init(&smp->nodes[0].next, 0); // assumed inititalized in original example
+
+       atomic_store(&smp->head, head);
+       atomic_store(&smp->tail, tail);
+       atomic_store(&smp->nodes[1].next, next);
 
        /* initialize avail list */
-       for (i=2; i<MAX_NODES; i++) {
-               smp->nodes[i].next.sep.ptr = i+1;
-               smp->nodes[i].next.sep.count = 0;
-       }
-       smp->nodes[MAX_NODES].next.sep.ptr = NULL;
-       smp->nodes[MAX_NODES].next.sep.count = 0;
-
-       /* initialize queue contents */
-       if (initial_nodes > 0) {
-               for (i=2; i<initial_nodes+2; i++) {
-                       smp->nodes[i].value = i;
-                       smp->nodes[i-1].next.sep.ptr = i;
-                       smp->nodes[i].next.sep.ptr = NULL;
-               }
-               smp->head.sep.ptr = 1;
-               smp->tail.sep.ptr = 1 + initial_nodes;    
+       for (i = 2; i < MAX_NODES; i++) {
+               next = MAKE_POINTER(i + 1, 0);
+               atomic_store(&smp->nodes[i].next, next);
        }
+
+       next = MAKE_POINTER(0, 0); // (NULL, 0)
+       atomic_store(&smp->nodes[MAX_NODES].next, next);
 }
 
-void enqueue(unsigned val)
+void enqueue(unsigned int val)
 {
-       unsigned success;
-       unsigned node;
-       pointer_t tail;
-       pointer_t next;
+       unsigned int success = 0;
+       unsigned int node;
+       pointer tail;
+       pointer next;
+       pointer tmp;
 
        node = new_node();
        smp->nodes[node].value = val;
-       smp->nodes[node].next.sep.ptr = NULL;
+       tmp = atomic_load(&smp->nodes[node].next);
+       set_ptr(&tmp, 0); // NULL
+       atomic_store(&smp->nodes[node].next, tmp);
 
-       for (success = FALSE; success == FALSE; ) {
-               tail.con = smp->tail.con;
-               next.con = smp->nodes[tail.sep.ptr].next.con;
-               if (tail.con == smp->tail.con) {
-                       if (next.sep.ptr == NULL) {
-                               success = cas(&smp->nodes[tail.sep.ptr].next, 
-                                               next.con,
-                                               MAKE_LONG(node, next.sep.count+1));
+       while (!success) {
+               tail = atomic_load(&smp->tail);
+               next = atomic_load(&smp->nodes[get_ptr(tail)].next);
+               if (tail == atomic_load(&smp->tail)) {
+                       if (get_ptr(next) == 0) { // == NULL
+                               pointer val = MAKE_POINTER(node, get_count(next) + 1);
+                               success = atomic_compare_exchange_weak(&smp->nodes[get_ptr(tail)].next,
+                                               &next,
+                                               val);
                        }
-                       if (success == FALSE) {
-                               cas(&smp->tail,
-                                               tail.con,
-                                               MAKE_LONG(smp->nodes[tail.sep.ptr].next.sep.ptr,
-                                                       tail.sep.count+1));
+                       if (!success) {
+                               unsigned int ptr = get_ptr(atomic_load(&smp->nodes[get_ptr(tail)].next));
+                               pointer val = MAKE_POINTER(ptr,
+                                               get_count(tail) + 1);
+                               atomic_compare_exchange_strong(&smp->tail,
+                                               &tail,
+                                               val);
                                thrd_yield();
                        }
                }
        }
-       cas(&smp->tail, 
-                       tail.con,
-                       MAKE_LONG(node, tail.sep.count+1));
+       atomic_compare_exchange_strong(&smp->tail,
+                       &tail,
+                       MAKE_POINTER(node, get_count(tail) + 1));
 }
 
-unsigned dequeue()
+unsigned int dequeue()
 {
-       unsigned value;
-       unsigned success;
-       pointer_t head;
-       pointer_t tail;
-       pointer_t next;
+       unsigned int value;
+       unsigned int success;
+       pointer head;
+       pointer tail;
+       pointer next;
 
        for (success = FALSE; success == FALSE; ) {
-               head.con = smp->head.con;
-               tail.con = smp->tail.con;
-               next.con = smp->nodes[head.sep.ptr].next.con;
-               if (smp->head.con == head.con) {
-                       if (head.sep.ptr == tail.sep.ptr) {
-                               if (next.sep.ptr == NULL) {
-                                       return NULL;
+               head = atomic_load(&smp->head);
+               tail = atomic_load(&smp->tail);
+               next = atomic_load(&smp->nodes[get_ptr(head)].next);
+               if (atomic_load(&smp->head) == head) {
+                       if (get_ptr(head) == get_ptr(tail)) {
+                               if (get_ptr(next) == 0) { // NULL
+                                       return 0; // NULL
                                }
-                               cas(&smp->tail,
-                                               tail.con,
-                                               MAKE_LONG(next.sep.ptr, tail.sep.count+1));
+                               atomic_compare_exchange_weak(&smp->tail,
+                                               &tail,
+                                               MAKE_POINTER(get_ptr(next), get_count(tail) + 1));
                                thrd_yield();
                        } else {
-                               value = smp->nodes[next.sep.ptr].value;
-                               success = cas(&smp->head,
-                                               head.con,
-                                               MAKE_LONG(next.sep.ptr, head.sep.count+1));
+                               value = smp->nodes[get_ptr(next)].value;
+                               success = atomic_compare_exchange_weak(&smp->head,
+                                               &head,
+                                               MAKE_POINTER(get_ptr(next), get_count(head) + 1));
                                if (success == FALSE) {
                                        thrd_yield();
                                }
                        }
                }
        }
-       reclaim(head.sep.ptr);
+       reclaim(get_ptr(head));
        return value;
 }
index 3e3f435..519e9e3 100644 (file)
@@ -3,41 +3,43 @@
 #define TRUE                           1
 #define FALSE                          0
 
-#define MAX_NODES                      0xff
+#define MAX_NODES                      0xf
 #define MAX_SERIAL                     10000
 
-#define MAKE_LONG(lo, hi)              ((hi)<<16)+(lo)
+typedef unsigned long long pointer;
+typedef atomic_ullong pointer_t;
 
-typedef union pointer {
-       struct {
-               volatile unsigned short count;
-               volatile unsigned short ptr;
-       } sep;
-       atomic_ulong con;
-} pointer_t;
+#define MAKE_POINTER(ptr, count)       ((((pointer)count) << 32) | ptr)
+#define PTR_MASK 0xffffffffLL
+#define COUNT_MASK (0xffffffffLL << 32)
+
+static inline void set_count(pointer *p, unsigned int val) { *p = (*p & ~COUNT_MASK) | ((pointer)val << 32); }
+static inline void set_ptr(pointer *p, unsigned int val) { *p = (*p & ~PTR_MASK) | val; }
+static inline unsigned int get_count(pointer p) { return p & PTR_MASK; }
+static inline unsigned int get_ptr(pointer p) { return (p & COUNT_MASK) >> 32; }
 
 typedef struct node {
-       unsigned value;
+       unsigned int value;
        pointer_t next;
-       unsigned foo[30];
+       unsigned int foo[30];
 } node_t;
 
 typedef struct private {
-       unsigned node;
-       unsigned value;
-       unsigned serial[MAX_SERIAL];
+       unsigned int node;
+       unsigned int value;
+       unsigned int serial[MAX_SERIAL];
 } private_t;
 
 typedef struct shared_mem {
        pointer_t head;
-       unsigned foo1[31];
+       unsigned int foo1[31];
        pointer_t tail;
-       unsigned foo2[31];
+       unsigned int foo2[31];
        node_t nodes[MAX_NODES+1];
-       unsigned serial;
+       unsigned int serial;
 } shared_mem_t;
 
-void init_private();
+void init_private(int pid);
 void init_memory();
 void init_queue();
-unsigned dequeue();
+unsigned int dequeue();