svn commit: r272925 - head/sys/kern

[Marcel Moolenaar]

Author: marcel
Date: Sat Oct 11 02:02:58 2014
New Revision: 272925
URL: https://svnweb.freebsd.org/changeset/base/272925

Log:
  Turn WITNESS_COUNT into a tunable and sysctl. This allows adjusting
  the value without recompiling the kernel.  This is useful when
  recompiling is not possible as an immediate solution. When we run out
  of witness objects, witness is completely disabled. Not having an
  immediate solution can therefore be problematic.
  
  Submitted by:	Sreekanth Rupavatharam <rupavath at juniper.net>
  Obtained from:	Juniper Networks, Inc.

Modified:
  head/sys/kern/subr_witness.c

Modified: head/sys/kern/subr_witness.c
==============================================================================
--- head/sys/kern/subr_witness.c	Sat Oct 11 01:01:18 2014	(r272924)
+++ head/sys/kern/subr_witness.c	Sat Oct 11 02:02:58 2014	(r272925)
@@ -135,7 +135,6 @@ __FBSDID("$FreeBSD$");
 #ifndef WITNESS_COUNT
 #define	WITNESS_COUNT 		1536
 #endif
-#define	WITNESS_CHILDCOUNT 	(WITNESS_COUNT * 4)
 #define	WITNESS_HASH_SIZE	251	/* Prime, gives load factor < 2 */
 #define	WITNESS_PENDLIST	(1024 + MAXCPU)
 
@@ -155,7 +154,6 @@ __FBSDID("$FreeBSD$");
 
 #define	MAX_W_NAME	64
 
-#define	BADSTACK_SBUF_SIZE	(256 * WITNESS_COUNT)
 #define	FULLGRAPH_SBUF_SIZE	512
 
 /*
@@ -184,7 +182,7 @@ __FBSDID("$FreeBSD$");
 #define	WITNESS_ATOD(x)	(((x) & WITNESS_RELATED_MASK) << 2)
 
 #define	WITNESS_INDEX_ASSERT(i)						\
-	MPASS((i) > 0 && (i) <= w_max_used_index && (i) < WITNESS_COUNT)
+	MPASS((i) > 0 && (i) <= w_max_used_index && (i) < witness_count)
 
 static MALLOC_DEFINE(M_WITNESS, "Witness", "Witness");
 
@@ -416,6 +414,13 @@ int	witness_skipspin = 0;
 #endif
 SYSCTL_INT(_debug_witness, OID_AUTO, skipspin, CTLFLAG_RDTUN, &witness_skipspin, 0, "");
 
+/* tunable for Witness count */
+int witness_count = WITNESS_COUNT;
+int badstack_sbuf_size = WITNESS_COUNT * 256;
+
+SYSCTL_INT(_debug_witness, OID_AUTO, witness_count, CTLFLAG_RDTUN, 
+    &witness_count, 0, "");
+
 /*
  * Call this to print out the relations between locks.
  */
@@ -450,7 +455,7 @@ SYSCTL_INT(_debug_witness, OID_AUTO, sle
     "");
 
 static struct witness *w_data;
-static uint8_t w_rmatrix[WITNESS_COUNT+1][WITNESS_COUNT+1];
+static uint8_t **w_rmatrix;
 static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT];
 static struct witness_hash w_hash;	/* The witness hash table. */
 
@@ -726,9 +731,18 @@ witness_initialize(void *dummy __unused)
 	struct witness *w, *w1;
 	int i;
 
-	w_data = malloc(sizeof (struct witness) * WITNESS_COUNT, M_WITNESS,
+	w_data = malloc(sizeof (struct witness) * witness_count, M_WITNESS,
 	    M_NOWAIT | M_ZERO);
 
+	w_rmatrix = malloc(sizeof(uint8_t *) * (witness_count+1),
+	    M_WITNESS, M_NOWAIT | M_ZERO);
+
+	for(i = 0; i < witness_count+1; i++) {
+		w_rmatrix[i] = malloc(sizeof(uint8_t) * (witness_count + 1), 
+		    M_WITNESS, M_NOWAIT | M_ZERO);
+	}
+	badstack_sbuf_size = witness_count * 256;
+	
 	/*
 	 * We have to release Giant before initializing its witness
 	 * structure so that WITNESS doesn't get confused.
@@ -739,7 +753,7 @@ witness_initialize(void *dummy __unused)
 	CTR1(KTR_WITNESS, "%s: initializing witness", __func__);
 	mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET |
 	    MTX_NOWITNESS | MTX_NOPROFILE);
-	for (i = WITNESS_COUNT - 1; i >= 0; i--) {
+	for (i = witness_count - 1; i >= 0; i--) {
 		w = &w_data[i];
 		memset(w, 0, sizeof(*w));
 		w_data[i].w_index = i;	/* Witness index never changes. */
@@ -752,8 +766,10 @@ witness_initialize(void *dummy __unused)
 	STAILQ_REMOVE_HEAD(&w_free, w_list);
 	w_free_cnt--;
 
-	memset(w_rmatrix, 0,
-	    (sizeof(**w_rmatrix) * (WITNESS_COUNT+1) * (WITNESS_COUNT+1)));
+	for(i = 0; i < witness_count; i++) {
+		memset(w_rmatrix[i], 0, sizeof(uint8_t) * 
+		    (witness_count + 1));
+	}
 
 	for (i = 0; i < LOCK_CHILDCOUNT; i++)
 		witness_lock_list_free(&w_locklistdata[i]);
@@ -1196,7 +1212,7 @@ witness_checkorder(struct lock_object *l
 	for (j = 0, lle = lock_list; lle != NULL; lle = lle->ll_next) {
 		for (i = lle->ll_count - 1; i >= 0; i--, j++) {
 
-			MPASS(j < WITNESS_COUNT);
+			MPASS(j < witness_count);
 			lock1 = &lle->ll_children[i];
 
 			/*
@@ -2057,7 +2073,7 @@ witness_get(void)
 	w_free_cnt--;
 	index = w->w_index;
 	MPASS(index > 0 && index == w_max_used_index+1 &&
-	    index < WITNESS_COUNT);
+	    index < witness_count);
 	bzero(w, sizeof(*w));
 	w->w_index = index;
 	if (index > w_max_used_index)
@@ -2482,7 +2498,7 @@ sysctl_debug_witness_badstacks(SYSCTL_HA
 		return (error);
 	}
 	error = 0;
-	sb = sbuf_new(NULL, NULL, BADSTACK_SBUF_SIZE, SBUF_AUTOEXTEND);
+	sb = sbuf_new(NULL, NULL, badstack_sbuf_size, SBUF_AUTOEXTEND);
 	if (sb == NULL)
 		return (ENOMEM);