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

lib/libzfs/libzfs.abi

@@ -6117,7 +6117,9 @@
       <enumerator name='VDEV_PROP_TRIM_SUPPORT' value='49'/>
       <enumerator name='VDEV_PROP_TRIM_ERRORS' value='50'/>
       <enumerator name='VDEV_PROP_SLOW_IOS' value='51'/>
-      <enumerator name='VDEV_NUM_PROPS' value='52'/>
+      <enumerator name='VDEV_PROP_SIT_OUT' value='52'/>
+      <enumerator name='VDEV_PROP_AUTOSIT' value='53'/>
+      <enumerator name='VDEV_NUM_PROPS' value='54'/>
     </enum-decl>
     <typedef-decl name='vdev_prop_t' type-id='1573bec8' id='5aa5c90c'/>
     <class-decl name='zpool_load_policy' size-in-bits='256' is-struct='yes' visibility='default' id='2f65b36f'>

lib/libzfs/libzfs_pool.c

@@ -5549,6 +5549,8 @@ zpool_get_vdev_prop_value(nvlist_t *nvprop, vdev_prop_t prop, char *prop_name,
 			/* Only use if provided by the RAIDZ VDEV above */
 			if (prop == VDEV_PROP_RAIDZ_EXPANDING)
 				return (ENOENT);
+			if (prop == VDEV_PROP_SIT_OUT)
+				return (ENOENT);
 		}
 		if (vdev_prop_index_to_string(prop, intval,
 		    (const char **)&strval) != 0)
@@ -5718,8 +5720,16 @@ zpool_set_vdev_prop(zpool_handle_t *zhp, const char *vdevname,
 	nvlist_free(nvl);
 	nvlist_free(outnvl);
 
-	if (ret)
-		(void) zpool_standard_error(zhp->zpool_hdl, errno, errbuf);
+	if (ret) {
+		if (errno == ENOTSUP) {
+			zfs_error_aux(zhp->zpool_hdl, dgettext(TEXT_DOMAIN,
+			    "property not supported for this vdev"));
+			(void) zfs_error(zhp->zpool_hdl, EZFS_PROPTYPE, errbuf);
+		} else {
+			(void) zpool_standard_error(zhp->zpool_hdl, errno,
+			    errbuf);
+		}
+	}
 
 	return (ret);
 }

lib/libzfs/libzfs_util.c

@@ -776,6 +776,11 @@ zpool_standard_error_fmt(libzfs_handle_t *hdl, int error, const char *fmt, ...)
 	case ZFS_ERR_ASHIFT_MISMATCH:
 		zfs_verror(hdl, EZFS_ASHIFT_MISMATCH, fmt, ap);
 		break;
+	case ZFS_ERR_TOO_MANY_SITOUTS:
+		zfs_error_aux(hdl, dgettext(TEXT_DOMAIN, "too many disks "
+		    "already sitting out"));
+		zfs_verror(hdl, EZFS_BUSY, fmt, ap);
+		break;
 	default:
 		zfs_error_aux(hdl, "%s", zfs_strerror(error));
 		zfs_verror(hdl, EZFS_UNKNOWN, fmt, ap);