sbp2:
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@xxxxxxxxxxxxxxxxx>
--- linux-2.6.14-rc1.orig/drivers/ieee1394/sbp2.c 2005-09-13 05:12:09.000000000 +0200
+++ linux-2.6.14-rc1/drivers/ieee1394/sbp2.c 2005-09-17 16:51:56.000000000 +0200
@@ -97,16 +97,18 @@ static char version[] __devinitdata =
*/
static int max_speed = IEEE1394_SPEED_MAX;
module_param(max_speed, int, 0644);
-MODULE_PARM_DESC(max_speed, "Force max speed (3 = 800mb, 2 = 400mb default, 1 = 200mb, 0 = 100mb)");
+MODULE_PARM_DESC(max_speed, "Force max speed (3 = 800mb, 2 = 400mb, 1 = 200mb, 0 = 100mb)");
/*
* Set serialize_io to 1 if you'd like only one scsi command sent
* down to us at a time (debugging). This might be necessary for very
* badly behaved sbp2 devices.
+ *
+ * TODO: Make this configurable per device.
*/
-static int serialize_io;
+static int serialize_io = 1;
module_param(serialize_io, int, 0444);
-MODULE_PARM_DESC(serialize_io, "Serialize all I/O coming down from the scsi drivers (default = 0)");
+MODULE_PARM_DESC(serialize_io, "Serialize I/O coming from scsi drivers (default = 1, faster = 0)");
/*
* Bump up max_sectors if you'd like to support very large sized
@@ -2837,7 +2859,8 @@ static int sbp2_module_init(void)
/* Module load debug option to force one command at a time (serializing I/O) */
if (serialize_io) {
- SBP2_ERR("Driver forced to serialize I/O (serialize_io = 1)");
+ SBP2_INFO("Driver forced to serialize I/O (serialize_io=1)");
+ SBP2_INFO("Try serialize_io=0 for better performance");
scsi_driver_template.can_queue = 1;
scsi_driver_template.cmd_per_lun = 1;
}
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