scsi: mpt3sas: lockless command submission
Performance improvement using block layer tag. Curent driver gets scsiio tracker and free smid from link list and array based tracking managed by driver. Accessing list in main io path is performance pentaly because of protection using spinlock "scsi_lookup_lock". In this patch: 1. Driver removes all link list access from main io path and use scmd->request->tag to get free smid. 2. Instead of holding 'struct scsiio_tracker' in its own pool driver can embed it into the scsi command. Driver provides cmd_size in scsi_host_template, so that struct scsiio_tracker is preallocated by scsi mid layer for each scsi command. Signed-off-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Suganath Prabu S <suganath-prabu.subramani@broadcom.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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