Detect a slow raidz child during reads

A single slow responding disk can affect the overall read
performance of a raidz group.  When a raidz child disk is
determined to be a persistent slow outlier, then have it
sit out during reads for a period of time. The raidz group
can use parity to reconstruct the data that was skipped.

Each time a slow disk is placed into a sit out period, its
`vdev_stat.vs_slow_ios count` is incremented and a zevent
class `ereport.fs.zfs.delay` is posted.

The length of the sit out period can be changed using the
`raid_read_sit_out_secs` module parameter.  Setting it to
zero disables slow outlier detection.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Dagnelie <paul.dagnelie@klarasystems.com>
Contributions-by: Don Brady <don.brady@klarasystems.com>
Contributions-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #17227

include/os/freebsd/spl/sys/time.h

@@ -62,6 +62,17 @@ typedef longlong_t	hrtime_t;
 #define	SEC_TO_TICK(sec)	((sec) * hz)
 #define	NSEC_TO_TICK(nsec)	((nsec) / (NANOSEC / hz))
 
+static __inline hrtime_t
+getlrtime(void)
+{
+	struct timespec ts;
+	hrtime_t nsec;
+
+	getnanouptime(&ts);
+	nsec = ((hrtime_t)ts.tv_sec * NANOSEC) + ts.tv_nsec;
+	return (nsec);
+}
+
 static __inline hrtime_t
 gethrtime(void)
 {

include/os/linux/spl/sys/time.h

@@ -79,6 +79,14 @@ gethrestime_sec(void)
 	return (ts.tv_sec);
 }
 
+static inline hrtime_t
+getlrtime(void)
+{
+	inode_timespec_t ts;
+	ktime_get_coarse_ts64(&ts);
+	return (((hrtime_t)ts.tv_sec * NSEC_PER_SEC) + ts.tv_nsec);
+}
+
 static inline hrtime_t
 gethrtime(void)
 {