Run a revision of the devstat interface:

Kernel:

Change statistics to use the *uptime() timescale (ie: relative to
boottime) rather than the UTC aligned timescale.  This makes the
device statistics code oblivious to clock steps.

Change timestamps to bintime format, they are cheaper.

Remove the "busy_count", and replace it with two counter fields:
"start_count" and "end_count", which are updated in the down and
up paths respectively.  This removes the locking constraint on
devstat.

Add a timestamp argument to devstat_start_transaction(), this will
normally be a timestamp set by the *_bio() function in bp->bio_t0.
Use this field to calculate duration of I/O operations.

Add two timestamp arguments to devstat_end_transaction(), one is
the current time, a NULL pointer means "take timestamp yourself",
the other is the timestamp of when this transaction started (see
above).

Change calculation of busy_time to operate on "the salami principle":
Only when we are idle, which we can determine by the start+end
counts being identical, do we update the "busy_from" field in the
down path.  In the up path we accumulate the timeslice in busy_time
and update busy_from.

Change the byte_* and num_* fields into two arrays: bytes[] and
operations[].

Userland:

Change the misleading "busy_time" name to be called "snap_time" and
make the time long double since that is what most users need anyway,
fill it using clock_gettime(CLOCK_MONOTONIC) to put it on the same
timescale as the kernel fields.

Change devstat_compute_etime() to operate on struct bintime.

Remove the version 2 legacy interface: the change to bintime makes
compatibility far too expensive.

Fix a bug in systat's "vm" page where boot relative busy times would
be bogus.

Bump __FreeBSD_version to 500107

Review & Collaboration by:	ken

1 files changed, 5 insertions, 4 deletions

diff --git a/libexec/rpc.rstatd/rstat_proc.c b/libexec/rpc.rstatd/rstat_proc.c
index bb04c16b75a2..440bdb6f588b 100644
--- a/libexec/rpc.rstatd/rstat_proc.c
+++ b/libexec/rpc.rstatd/rstat_proc.c
@@ -370,7 +370,7 @@ haveadisk(void)
 void
 updatexfers(int numdevs, int *devs)
 {
-	register int i, j, t;
+	register int i, j, k, t;
 	struct statinfo stats;
 	int num_devices = 0;
 	u_int64_t total_transfers;
@@ -400,9 +400,10 @@ updatexfers(int numdevs, int *devs)
 		      & DEVSTAT_TYPE_MASK) == DEVSTAT_TYPE_DIRECT)
 		 && ((stats.dinfo->devices[i].device_type
 		      & DEVSTAT_TYPE_PASS) == 0)) {
-			total_transfers = stats.dinfo->devices[i].num_reads +
-					  stats.dinfo->devices[i].num_writes +
-					  stats.dinfo->devices[i].num_other;
+			total_transfers = 0;
+			for (k = 0; k < DEVSTAT_N_TRANS_FLAGS; k++)
+				total_transfers +=
+				    stats.dinfo->devices[i].operations[k];
 			/*
 			 * XXX KDM If the total transfers for this device
 			 * are greater than the amount we can fit in a