Revert to open hashing. It makes the code simpler, and works farily well

even when the number of records approaches the size of the hash table.
Besides, the previous implementation (using linear probing) was broken :)

Also, use the newly introduced MTX_SYSINIT.

1 files changed, 10 insertions, 16 deletions

diff --git a/sys/kern/kern_mutex.c b/sys/kern/kern_mutex.c
index 3207ee1..fe8560a 100644
--- a/sys/kern/kern_mutex.c
+++ b/sys/kern/kern_mutex.c
@@ -219,6 +219,7 @@ struct mutex_prof {
 #define MPROF_CNT 2
 #define MPROF_AVG 3
 	u_int64_t counter[4];
+	struct mutex_prof *next;
 };
 
 /*
@@ -227,10 +228,10 @@ struct mutex_prof {
  *
  * Note: NUM_MPROF_BUFFERS must be smaller than MPROF_HASH_SIZE.
  */
-#define NUM_MPROF_BUFFERS 4096
+#define NUM_MPROF_BUFFERS 1000
 static struct mutex_prof mprof_buf[NUM_MPROF_BUFFERS];
 static int first_free_mprof_buf;
-#define MPROF_HASH_SIZE 32771
+#define MPROF_HASH_SIZE 1009
 static struct mutex_prof *mprof_hash[MPROF_HASH_SIZE];
 
 static int mutex_prof_acquisitions;
@@ -256,13 +257,7 @@ SYSCTL_INT(_debug_mutex_prof, OID_AUTO, collisions, CTLFLAG_RD,
  * mprof_mtx protects the profiling buffers and the hash.
  */
 static struct mtx mprof_mtx;
-
-static void
-mprof_init(void *arg __unused)
-{
-	mtx_init(&mprof_mtx, "mutex profiling lock", MTX_SPIN | MTX_QUIET);
-}
-SYSINIT(mprofinit, SI_SUB_LOCK, SI_ORDER_ANY, mprof_init, NULL);
+MTX_SYSINIT(mprof, &mprof_mtx, "mutex profiling lock", MTX_SPIN | MTX_QUIET);
 
 static u_int64_t
 nanoseconds(void)
@@ -340,7 +335,7 @@ _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line)
 		struct mutex_prof *mpp;
 		u_int64_t acqtime, now;
 		const char *p, *q;
-		volatile u_int hash, n;
+		volatile u_int hash;
 
 		now = nanoseconds();
 		acqtime = m->acqtime;
@@ -354,12 +349,9 @@ _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line)
 		for (hash = line, q = p; *q != '\0'; ++q)
 			hash = (hash * 2 + *q) % MPROF_HASH_SIZE;
 		mtx_lock_spin(&mprof_mtx);
-		n = hash;
-		while ((mpp = mprof_hash[n]) != NULL) {
+		for (mpp = mprof_hash[hash]; mpp != NULL; mpp = mpp->next)
 			if (mpp->line == line && strcmp(mpp->file, p) == 0)
 				break;
-			n = (n + 1) % MPROF_HASH_SIZE;
-		}
 		if (mpp == NULL) {
 			/* Just exit if we cannot get a trace buffer */
 			if (first_free_mprof_buf >= NUM_MPROF_BUFFERS) {
@@ -370,9 +362,11 @@ _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line)
 			mpp->name = mtx_name(m);
 			mpp->file = p;
 			mpp->line = line;
-			mutex_prof_collisions += n - hash;
+			mpp->next = mprof_hash[hash];
+			if (mprof_hash[hash] != NULL)
+				++mutex_prof_collisions;
+			mprof_hash[hash] = mpp;	
 			++mutex_prof_records;
-			mprof_hash[hash] = mpp;
 		}
 		/*
 		 * Record if the mutex has been held longer now than ever