From ae4f863c8949e1c26ce704b09f53df54c5c63f61 Mon Sep 17 00:00:00 2001
From: Ian Lepore <ian@FreeBSD.org>
Date: Sat, 19 Jan 2013 00:50:12 +0000
Subject: [PATCH] Eliminate the need for an intermediate array of indices into
 the arrays of interrupt counts and names, by making the names into an array
 of fixed-length strings that can be directly indexed.  This eliminates extra
 memory accesses on every interrupt to increment the counts.

As a side effect, it also fixes a bug that would corrupt the names data
if a name was longer than MAXCOMLEN, which led to incorrect vmstat -i output.

Approved by:	cognet (mentor)
---
 sys/arm/arm/intr.c     | 36 ++++++++++++++++++++++++------------
 sys/arm/arm/machdep.c  |  1 +
 sys/arm/include/intr.h |  1 +
 3 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/sys/arm/arm/intr.c b/sys/arm/arm/intr.c
index e79e44c70aa7..18a52a731095 100644
--- a/sys/arm/arm/intr.c
+++ b/sys/arm/arm/intr.c
@@ -50,23 +50,40 @@ __FBSDID("$FreeBSD$");
 #include <machine/intr.h>
 #include <machine/cpu.h>
 
+#define	INTRNAME_LEN	(MAXCOMLEN + 1)
+
 typedef void (*mask_fn)(void *);
 
 static struct intr_event *intr_events[NIRQ];
-static int intrcnt_tab[NIRQ];
-static int intrcnt_index = 0;
-static int last_printed = 0;
 
 void	arm_handler_execute(struct trapframe *, int);
 
 void (*arm_post_filter)(void *) = NULL;
 
+/*
+ * Pre-format intrnames into an array of fixed-size strings containing spaces.
+ * This allows us to avoid the need for an intermediate table of indices into
+ * the names and counts arrays, while still meeting the requirements and
+ * assumptions of vmstat(8) and the kdb "show intrcnt" command, the two
+ * consumers of this data.
+ */
+void
+arm_intrnames_init()
+{
+	int i;
+
+	memset(intrnames, ' ', NIRQ * INTRNAME_LEN);
+	for (i = 0; i < NIRQ; ++i)
+		intrnames[i * INTRNAME_LEN - 1] = 0;
+}
+
 void
 arm_setup_irqhandler(const char *name, driver_filter_t *filt,
     void (*hand)(void*), void *arg, int irq, int flags, void **cookiep)
 {
 	struct intr_event *event;
 	int error;
+	char namebuf[INTRNAME_LEN];
 
 	if (irq < 0 || irq >= NIRQ)
 		return;
@@ -78,14 +95,9 @@ arm_setup_irqhandler(const char *name, driver_filter_t *filt,
 		if (error)
 			return;
 		intr_events[irq] = event;
-		last_printed +=
-		    snprintf(intrnames + last_printed,
-		    MAXCOMLEN + 1,
-		    "irq%d: %s", irq, name);
-		last_printed++;
-		intrcnt_tab[irq] = intrcnt_index;
-		intrcnt_index++;
-		
+		snprintf(namebuf, sizeof(namebuf), "irq%d: %s", irq, name);
+		sprintf(intrnames + INTRNAME_LEN * irq, "%-*s", 
+		    INTRNAME_LEN - 1, namebuf);
 	}
 	intr_event_add_handler(event, name, filt, hand, arg,
 	    intr_priority(flags), flags, cookiep);
@@ -122,7 +134,7 @@ arm_handler_execute(struct trapframe *frame, int irqnb)
 	PCPU_INC(cnt.v_intr);
 	i = -1;
 	while ((i = arm_get_next_irq(i)) != -1) {
-		intrcnt[intrcnt_tab[i]]++;
+		intrcnt[i]++;
 		event = intr_events[i];
 		if (intr_event_handle(event, frame) != 0) {
 			/* XXX: Log stray IRQs */
diff --git a/sys/arm/arm/machdep.c b/sys/arm/arm/machdep.c
index a1b5a8fdb2c4..5c4d92c6a2c0 100644
--- a/sys/arm/arm/machdep.c
+++ b/sys/arm/arm/machdep.c
@@ -1474,6 +1474,7 @@ initarm(struct arm_boot_params *abp)
 
 	init_proc0(kernelstack.pv_va);
 
+	arm_intrnames_init();
 	arm_vector_init(ARM_VECTORS_HIGH, ARM_VEC_ALL);
 	arm_dump_avail_init(memsize, sizeof(dump_avail) / sizeof(dump_avail[0]));
 	pmap_bootstrap(freemempos, pmap_bootstrap_lastaddr, &kernel_l1pt);
diff --git a/sys/arm/include/intr.h b/sys/arm/include/intr.h
index 45e36e917d69..939296905de3 100644
--- a/sys/arm/include/intr.h
+++ b/sys/arm/include/intr.h
@@ -70,6 +70,7 @@
 int arm_get_next_irq(int);
 void arm_mask_irq(uintptr_t);
 void arm_unmask_irq(uintptr_t);
+void arm_intrnames_init(void);
 void arm_setup_irqhandler(const char *, int (*)(void*), void (*)(void*),
     void *, int, int, void **);
 int arm_remove_irqhandler(int, void *);