[PATCH] remove duplicated disk statistics

This patch will break some userspace monitoring apps in the name of
having sane disk statistics in 2.6.x.

Patch from Rick Lindsley <ricklind@us.ibm.com>

In 2.5.46, there are now disk statistics being collected twice: once
for gendisk/hd_struct, and once for dkstat.  They are collecting the
same thing.  This patch removes dkstat, which also had the disadvantage
of being limited by DK_MAX_MAJOR and DK_MAX_DISK. (Those #defines are
removed too.)

In addition, this patch removes disk statistics from /proc/stat since
they are now available via sysfs and there seems to have been a general
preference in previous discussions to "clean up" /proc/stat.  Too many
disks being reported in /proc/stat also caused buffer overflows when
trying to print out the data.

The code in led.c from the parisc architecture has not apparently been
recompiled under recent versions of 2.5, since it references
kstat.dk_drive which doesn't exist in later versions.  Accordingly,
I've added an #ifdef 0 and a comment to that code so that it may at
least compile, albeit without one feature -- a step up from its state
now.  If it is preferable to keep the broken code in, that patch may
easily be excised from below.

drivers/block/ll_rw_blk.c

@@ -27,11 +27,6 @@
 #include <linux/completion.h>
 #include <linux/slab.h>
 
-/*
- * Disk stats 
- */
-struct disk_stat dkstat;
-
 /*
  * For the allocated request tables
  */
@@ -1412,19 +1407,6 @@ void drive_stat_acct(struct request *rq, int nr_sectors, int new_io)
 
 	major = rq->rq_disk->major;
 	index = rq->rq_disk->first_minor >> rq->rq_disk->minor_shift;
-
-	if ((index >= DK_MAX_DISK) || (major >= DK_MAX_MAJOR))
-		return;
-
-	dkstat.drive[major][index] += new_io;
-	if (rw == READ) {
-		dkstat.drive_rio[major][index] += new_io;
-		dkstat.drive_rblk[major][index] += nr_sectors;
-	} else if (rw == WRITE) {
-		dkstat.drive_wio[major][index] += new_io;
-		dkstat.drive_wblk[major][index] += nr_sectors;
-	} else
-		printk(KERN_ERR "drive_stat_acct: cmd not R/W?\n");
 }
 
 /*

drivers/parisc/led.c

@@ -404,6 +404,14 @@ static void led_get_diskio_stats(int addvalue)
 	int major, disk, total;
 	
 	total = 0;
+#ifdef 0
+	/*
+	 * this section will no longer work in 2.5, as we no longer
+	 * have either kstat.dk_drive nor DK_MAX_*.  It can probably
+	 * be rewritten to use the per-disk statistics now kept in the
+	 * gendisk, but since I have no HP machines to test it on, I'm
+	 * not really up to that.  ricklind@us.ibm.com 11/7/02
+	 */
 	for (major = 0; major < DK_MAX_MAJOR; major++) {
 	    for (disk = 0; disk < DK_MAX_DISK; disk++)
 		total += dkstat.drive[major][disk];
@@ -417,6 +425,7 @@ static void led_get_diskio_stats(int addvalue)
 	    } else
 		led_diskio_counter += CALC_ADD(total, diskio_max, addvalue);
 	}
+#endif
 	
 	diskio_total_last += total; 
 }

fs/proc/proc_misc.c

@@ -330,7 +330,6 @@ static int kstat_read_proc(char *page, char **start, off_t off,
 	extern unsigned long total_forks;
 	unsigned long jif = jiffies;
 	unsigned int sum = 0, user = 0, nice = 0, system = 0, idle = 0, iowait = 0;
-	int major, disk;
 
 	for (i = 0 ; i < NR_CPUS; i++) {
 		int j;
@@ -370,26 +369,6 @@ static int kstat_read_proc(char *page, char **start, off_t off,
 		len += sprintf(page + len, " %u", kstat_irqs(i));
 #endif
 
-	len += sprintf(page + len, "\ndisk_io: ");
-
-	for (major = 0; major < DK_MAX_MAJOR; major++) {
-		for (disk = 0; disk < DK_MAX_DISK; disk++) {
-			int active = dkstat.drive[major][disk] +
-				dkstat.drive_rblk[major][disk] +
-				dkstat.drive_wblk[major][disk];
-			if (active)
-				len += sprintf(page + len,
-					"(%u,%u):(%u,%u,%u,%u,%u) ",
-					major, disk,
-					dkstat.drive[major][disk],
-					dkstat.drive_rio[major][disk],
-					dkstat.drive_rblk[major][disk],
-					dkstat.drive_wio[major][disk],
-					dkstat.drive_wblk[major][disk]
-			);
-		}
-	}
-
 	len += sprintf(page + len,
 		"\nctxt %lu\n"
 		"btime %lu\n"

include/linux/blkdev.h

@@ -11,22 +11,6 @@
 
 #include <asm/scatterlist.h>
 
-/*
- * Disk stats ...
- */
-
-#define DK_MAX_MAJOR 16
-#define DK_MAX_DISK 16
- 
-struct disk_stat {
-        unsigned int drive[DK_MAX_MAJOR][DK_MAX_DISK];
-        unsigned int drive_rio[DK_MAX_MAJOR][DK_MAX_DISK];
-        unsigned int drive_wio[DK_MAX_MAJOR][DK_MAX_DISK];
-        unsigned int drive_rblk[DK_MAX_MAJOR][DK_MAX_DISK];
-        unsigned int drive_wblk[DK_MAX_MAJOR][DK_MAX_DISK];
-};
-extern struct disk_stat dkstat;
-
 struct request_queue;
 typedef struct request_queue request_queue_t;
 struct elevator_s;