[SCSI] aacraid: 17 element sg performance update
Received From Mark Salyzyn.
The Jaguar and Corsair class of adapters (2410, 2810, 2610, 21610, CERC)
perform better (about 10% better read performance, write performance
neutral) with current Firmware if the OS limits the number of scatter
gather elements to 17 per request.
Signed-off-by: Mark Haverkamp <markh@osdl.org>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/drivers/scsi/aacraid/aacraid.h b/drivers/scsi/aacraid/aacraid.h
index 30fd8d6..66dbb6d 100644
--- a/drivers/scsi/aacraid/aacraid.h
+++ b/drivers/scsi/aacraid/aacraid.h
@@ -532,6 +532,13 @@
#define AAC_QUIRK_MASTER 0x0008
/*
+ * Some adapter firmware perform poorly when it must split up scatter gathers
+ * in order to deal with the limits of the underlying CHIM. This limit in this
+ * class of adapters is 17 scatter gather elements.
+ */
+#define AAC_QUIRK_17SG 0x0010
+
+/*
* The adapter interface specs all queues to be located in the same
* physically contigous block. The host structure that defines the
* commuication queues will assume they are each a separate physically