mpt2sas: Add free smids to the head, not tail of list

Reusing a smid quickly means it's still cache-hot.  This yields a small
but noticable performance improvement in a well-known database benchmark.
This improvement is already present in the mpt3sas driver.

Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
Reviewed-by: Nicholas Bellinger <nab@linux-iscsi.org>
Reviewed-by: Praveen Krishnamoorthy <Praveen.krishnamoorthy@lsi.com>
Acked-by: Sreekanth Reddy <Sreekanth.reddy@lsi.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/scsi/mpt2sas/mpt2sas_base.c b/drivers/scsi/mpt2sas/mpt2sas_base.c
index bde63f7..8b88118 100644 (file)
--- a/drivers/scsi/mpt2sas/mpt2sas_base.c
+++ b/drivers/scsi/mpt2sas/mpt2sas_base.c
@@ -1739,14 +1739,14 @@ mpt2sas_base_free_smid(struct MPT2SAS_ADAPTER *ioc, u16 smid)
                        list_for_each_entry_safe(chain_req, next,
                            &ioc->scsi_lookup[i].chain_list, tracker_list) {
                                list_del_init(&chain_req->tracker_list);
-                               list_add_tail(&chain_req->tracker_list,
+                               list_add(&chain_req->tracker_list,
                                    &ioc->free_chain_list);
                        }
                }
                ioc->scsi_lookup[i].cb_idx = 0xFF;
                ioc->scsi_lookup[i].scmd = NULL;
                ioc->scsi_lookup[i].direct_io = 0;
-               list_add_tail(&ioc->scsi_lookup[i].tracker_list,
+               list_add(&ioc->scsi_lookup[i].tracker_list,
                    &ioc->free_list);
                spin_unlock_irqrestore(&ioc->scsi_lookup_lock, flags);
 
@@ -1764,13 +1764,13 @@ mpt2sas_base_free_smid(struct MPT2SAS_ADAPTER *ioc, u16 smid)
                /* hi-priority */
                i = smid - ioc->hi_priority_smid;
                ioc->hpr_lookup[i].cb_idx = 0xFF;
-               list_add_tail(&ioc->hpr_lookup[i].tracker_list,
+               list_add(&ioc->hpr_lookup[i].tracker_list,
                    &ioc->hpr_free_list);
        } else if (smid <= ioc->hba_queue_depth) {
                /* internal queue */
                i = smid - ioc->internal_smid;
                ioc->internal_lookup[i].cb_idx = 0xFF;
-               list_add_tail(&ioc->internal_lookup[i].tracker_list,
+               list_add(&ioc->internal_lookup[i].tracker_list,
                    &ioc->internal_free_list);
        }
        spin_unlock_irqrestore(&ioc->scsi_lookup_lock, flags);