1 files changed, 83 insertions, 0 deletions
diff --git a/gc/include/private/specific.h b/gc/include/private/specific.h
new file mode 100644
index 0000000..60c152c
--- /dev/null
+++ b/gc/include/private/specific.h
@@ -0,0 +1,83 @@
+/*
+ * This is a reimplementation of a subset of the pthread_getspecific/setspecific
+ * interface. This appears to outperform the standard linuxthreads one
+ * by a significant margin.
+ * The major restriction is that each thread may only make a single
+ * pthread_setspecific call on a single key.  (The current data structure
+ * doesn't really require that.  The restriction should be easily removable.)
+ * We don't currently support the destruction functions, though that
+ * could be done.
+ * We also currently assume that only one pthread_setspecific call
+ * can be executed at a time, though that assumption would be easy to remove
+ * by adding a lock.
+ */
+
+#include <errno.h>
+
+/* Called during key creation or setspecific.		*/
+/* For the GC we already hold lock.			*/
+/* Currently allocated objects leak on thread exit.	*/
+/* That's hard to fix, but OK if we allocate garbage	*/
+/* collected memory.					*/
+#define MALLOC_CLEAR(n) GC_INTERNAL_MALLOC(n, NORMAL)
+#define PREFIXED(name) GC_##name
+
+#define TS_CACHE_SIZE 1024
+#define CACHE_HASH(n) (((((long)n) >> 8) ^ (long)n) & (TS_CACHE_SIZE - 1))
+#define TS_HASH_SIZE 1024
+#define HASH(n) (((((long)n) >> 8) ^ (long)n) & (TS_HASH_SIZE - 1))
+
+typedef struct thread_specific_entry {
+	unsigned long qtid;	/* quick thread id, only for cache */
+	void * value;
+	pthread_t thread;
+	struct thread_specific_entry *next;
+} tse;
+
+
+/* We represent each thread-specific datum as two tables.  The first is	*/
+/* a cache, index by a "quick thread identifier".  The "quick" thread	*/
+/* identifier is an easy to compute value, which is guaranteed to	*/
+/* determine the thread, though a thread may correspond to more than	*/
+/* one value.  We typically use the address of a page in the stack.	*/
+/* The second is a hash table, indexed by pthread_self().  It is used	*/
+/* only as a backup.							*/
+
+/* Return the "quick thread id".  Default version.  Assumes page size,	*/
+/* or at least thread stack separation, is at least 4K.			*/
+static __inline__ long quick_thread_id() {
+    int dummy;
+    return (long)(&dummy) >> 12;
+}
+
+#define INVALID_QTID ((unsigned long)(-1))
+
+typedef struct thread_specific_data {
+    tse * volatile cache[TS_CACHE_SIZE];
+			/* A faster index to the hash table */
+    tse * hash[TS_HASH_SIZE];
+    pthread_mutex_t lock;
+} tsd;
+
+typedef tsd * PREFIXED(key_t);
+
+extern int PREFIXED(key_create) (tsd ** key_ptr, void (* destructor)(void *));
+
+extern int PREFIXED(setspecific) (tsd * key, void * value);
+
+extern void PREFIXED(remove_specific) (tsd * key);
+
+/* An internal version of getspecific that assumes a cache miss.	*/
+void * PREFIXED(slow_getspecific) (tsd * key, unsigned long qtid,
+				   tse * volatile * cache_entry);
+
+static __inline__ void * PREFIXED(getspecific) (tsd * key) {
+    long qtid = quick_thread_id();
+    unsigned hash_val = CACHE_HASH(qtid);
+    tse * volatile * entry_ptr = key -> cache + hash_val;
+    tse * entry = *entry_ptr;   /* Must be loaded only once.	*/
+    if (entry -> qtid == qtid) return entry -> value;
+    return PREFIXED(slow_getspecific) (key, qtid, entry_ptr);
+}
+
+