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, 2 insertions, 2 deletions

diff --git a/sys/cam/cam_periph.c b/sys/cam/cam_periph.c
index 247ebb8..09126e6 100644
--- a/sys/cam/cam_periph.c
+++ b/sys/cam/cam_periph.c
@@ -866,7 +866,7 @@ cam_periph_runccb(union ccb *ccb,
 	 * this particular type of ccb, record the transaction start.
 	 */
 	if ((ds != NULL) && (ccb->ccb_h.func_code == XPT_SCSI_IO))
-		devstat_start_transaction(ds);
+		devstat_start_transaction(ds, NULL);
 
 	xpt_action(ccb);
  
@@ -896,7 +896,7 @@ cam_periph_runccb(union ccb *ccb,
 					CAM_DIR_NONE) ?  DEVSTAT_NO_DATA : 
 					(ccb->ccb_h.flags & CAM_DIR_OUT) ?
 					DEVSTAT_WRITE : 
-					DEVSTAT_READ);
+					DEVSTAT_READ, NULL, NULL);
 
 	return(error);
 }