scsi: efct: Decrease area under spinlock

Under the session level spinlock node->active_ios_lock in
efct_scsi_io_alloc() we are taking another spinlock for the port.  This
leads to contention between sessions and even between I/Os in the same
session.

Reduce the locked region to active_ios list for which active_ios_lock is
intended. Spinlock CPU usage decreases from 18% down to 13%. IOPS are
increased from 220 kIOPS to 264 kIOPS for one LUN.

Link: https://lore.kernel.org/r/20210914105539.6942-4-d.bogdanov@yadro.com
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Ram Vegesna <ram.vegesna@broadcom.com>
Signed-off-by: Dmitry Bogdanov <d.bogdanov@yadro.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/elx/efct/efct_scsi.c b/drivers/scsi/elx/efct/efct_scsi.c
index 40fb3a724c76d019ce14dc58e6679beca080300c..8535bb7eabd8e1abeb74c03b1fec8352e7441ee4 100644 (file)
--- a/drivers/scsi/elx/efct/efct_scsi.c
+++ b/drivers/scsi/elx/efct/efct_scsi.c
@@ -38,8 +38,6 @@ efct_scsi_io_alloc(struct efct_node *node)
 
        xport = efct->xport;
 
-       spin_lock_irqsave(&node->active_ios_lock, flags);
-
        io = efct_io_pool_io_alloc(efct->xport->io_pool);
        if (!io) {
                efc_log_err(efct, "IO alloc Failed\n");
@@ -66,6 +64,7 @@ efct_scsi_io_alloc(struct efct_node *node)
 
        /* Add to node's active_ios list */
        INIT_LIST_HEAD(&io->list_entry);
+       spin_lock_irqsave(&node->active_ios_lock, flags);
        list_add(&io->list_entry, &node->active_ios);
 
        spin_unlock_irqrestore(&node->active_ios_lock, flags);