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[PATCH] sbp2: default to serialize_io=1

Set serialize_io=1 by default. This is safer and required by seemingly more
and more hardware. It causes little or no performance loss for S400 devices.
Performance of S800 1394b devices may drop by 25...30%. Therefore make the
parameter's description and dmesg message clearer about performance impact.

Update description of the max_speed parameter too. IEEE1394_SPEED_MAX is
currently S800.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Jody McIntyre <scjody@steamballoon.com>
Cc: Ben Collins <bcollins@debian.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

authored by

Jody McIntyre and committed by
Linus Torvalds 2bab359a abd559b1

+7 -4
+7 -4
drivers/ieee1394/sbp2.c
··· 97 97 */ 98 98 static int max_speed = IEEE1394_SPEED_MAX; 99 99 module_param(max_speed, int, 0644); 100 - MODULE_PARM_DESC(max_speed, "Force max speed (3 = 800mb, 2 = 400mb default, 1 = 200mb, 0 = 100mb)"); 100 + MODULE_PARM_DESC(max_speed, "Force max speed (3 = 800mb, 2 = 400mb, 1 = 200mb, 0 = 100mb)"); 101 101 102 102 /* 103 103 * Set serialize_io to 1 if you'd like only one scsi command sent 104 104 * down to us at a time (debugging). This might be necessary for very 105 105 * badly behaved sbp2 devices. 106 + * 107 + * TODO: Make this configurable per device. 106 108 */ 107 - static int serialize_io; 109 + static int serialize_io = 1; 108 110 module_param(serialize_io, int, 0444); 109 - MODULE_PARM_DESC(serialize_io, "Serialize all I/O coming down from the scsi drivers (default = 0)"); 111 + MODULE_PARM_DESC(serialize_io, "Serialize I/O coming from scsi drivers (default = 1, faster = 0)"); 110 112 111 113 /* 112 114 * Bump up max_sectors if you'd like to support very large sized ··· 2859 2857 2860 2858 /* Module load debug option to force one command at a time (serializing I/O) */ 2861 2859 if (serialize_io) { 2862 - SBP2_ERR("Driver forced to serialize I/O (serialize_io = 1)"); 2860 + SBP2_INFO("Driver forced to serialize I/O (serialize_io=1)"); 2861 + SBP2_INFO("Try serialize_io=0 for better performance"); 2863 2862 scsi_driver_template.can_queue = 1; 2864 2863 scsi_driver_template.cmd_per_lun = 1; 2865 2864 }