[SCSI] fcoe: Add sysfs parameter to fcoe for minimum DDP read I/O size
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>
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@ -49,6 +49,12 @@ MODULE_AUTHOR("Open-FCoE.org");
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MODULE_DESCRIPTION("FCoE");
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MODULE_LICENSE("GPL v2");
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/* Performance tuning parameters for fcoe */
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static unsigned int fcoe_ddp_min;
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module_param_named(ddp_min, fcoe_ddp_min, uint, S_IRUGO | S_IWUSR);
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MODULE_PARM_DESC(ddp_min, "Minimum I/O size in bytes for " \
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"Direct Data Placement (DDP).");
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/* fcoe host list */
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LIST_HEAD(fcoe_hostlist);
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DEFINE_RWLOCK(fcoe_hostlist_lock);
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@ -414,7 +420,8 @@ static int fcoe_shost_config(struct fc_lport *lp, struct Scsi_Host *shost,
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*/
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bool fcoe_oem_match(struct fc_frame *fp)
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{
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return fc_fcp_is_read(fr_fsp(fp));
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return fc_fcp_is_read(fr_fsp(fp)) &&
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(fr_fsp(fp)->data_len > fcoe_ddp_min);
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}
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/**
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