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[SCSI] fcoe: Add sysfs parameter to fcoe for minimum DDP read I/O size

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This adds fcoe_ddp_min as a module parameter for fcoe module to:
/sys/module/fcoe/parameters/ddp_min

It is observed that for some hardware, particularly Intel 82599, there is too
much overhead in setting up context for direct data placement (DDP) read when
the requested read I/O size is small. This is added as a module parameter for
performance tuning and is set as 0 by default and user can change this based
on their own hardware.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
This commit is contained in:
Yi Zou 2009-08-25 13:59:03 -07:00 committed by James Bottomley
parent b2f0091fbf
commit 05cc739073
1 changed files with 8 additions and 1 deletions
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9
drivers/scsi/fcoe/fcoe.c
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@ -49,6 +49,12 @@ MODULE_AUTHOR("Open-FCoE.org");
MODULE_DESCRIPTION("FCoE");
MODULE_LICENSE("GPL v2");
/* Performance tuning parameters for fcoe */
static unsigned int fcoe_ddp_min;
module_param_named(ddp_min, fcoe_ddp_min, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(ddp_min, "Minimum I/O size in bytes for " \
"Direct Data Placement (DDP).");
/* fcoe host list */
LIST_HEAD(fcoe_hostlist);
DEFINE_RWLOCK(fcoe_hostlist_lock);
@ -414,7 +420,8 @@ static int fcoe_shost_config(struct fc_lport *lp, struct Scsi_Host *shost,
*/
bool fcoe_oem_match(struct fc_frame *fp)
{
return fc_fcp_is_read(fr_fsp(fp));
return fc_fcp_is_read(fr_fsp(fp)) &&
(fr_fsp(fp)->data_len > fcoe_ddp_min);
}
/**