Add enable_cmd_list flag in shost template to indicate scs.mq stack
to keep track of cmd_list per sdev.
Default behaviour is not to keep track of cmd_list per sdev, as this may
introduce
lock contention. (overhead is more on multi-node NUMA.)
Patch is tested using megaraid_sas driver with "enable_cmd_list" value set to 1
and 0.
Added MAINTAINER of Adaptec to verify changes.
Signed-off-by: Kashyap Desai <kashyap.de...@avagotech.com>
--
diff --git a/drivers/scsi/aacraid/linit.c b/drivers/scsi/aacraid/linit.c
index 63f576c..6cb5132 100644
--- a/drivers/scsi/aacraid/linit.c
+++ b/drivers/scsi/aacraid/linit.c
@@ -1082,6 +1082,7 @@ static struct scsi_host_template aac_driver_template = {
.use_clustering = ENABLE_CLUSTERING,
.emulated = 1,
.no_write_same = 1,
+ .enable_cmd_list = 1,
};
static void __aac_shutdown(struct aac_dev * aac)
diff --git a/drivers/scsi/dpt_i2o.c b/drivers/scsi/dpt_i2o.c
index 67283ef..3c91ba6 100644
--- a/drivers/scsi/dpt_i2o.c
+++ b/drivers/scsi/dpt_i2o.c
@@ -3565,6 +3565,7 @@ static struct scsi_host_template driver_template = {
.this_id = 7,
.cmd_per_lun = 1,
.use_clustering = ENABLE_CLUSTERING,
+ .enable_cmd_list = 1,
};
static int __init adpt_init(void)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 9c44392..a3ddaa5 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -645,16 +645,18 @@ static void scsi_mq_free_sgtables(struct scsi_cmnd *cmd)
static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd)
{
struct scsi_device *sdev = cmd->device;
+ struct Scsi_Host *shost = sdev->host;
unsigned long flags;
- BUG_ON(list_empty(&cmd->list));
-
scsi_mq_free_sgtables(cmd);
scsi_uninit_cmd(cmd);
- spin_lock_irqsave(&sdev->list_lock, flags);
- list_del_init(&cmd->list);
- spin_unlock_irqrestore(&sdev->list_lock, flags);
+ if (shost->hostt->enable_cmd_list) {
+ BUG_ON(list_empty(&cmd->list));
+ spin_lock_irqsave(&sdev->list_lock, flags);
+ list_del_init(&cmd->list);
+ spin_unlock_irqrestore(&sdev->list_lock, flags);
+ }
}
/*
@@ -1817,12 +1819,14 @@ static int scsi_mq_prep_fn(struct request *req)
cmd->jiffies_at_alloc = jiffies;
/*
- * XXX: cmd_list lookups are only used by two drivers, try to get
- * rid of this list in common code.
+ * XXX: cmd_list lookups are only used by two drivers. Try to
+ * reduce lock contention, managing sdev cmd_list for requested driver.
*/
- spin_lock_irq(&sdev->list_lock);
- list_add_tail(&cmd->list, &sdev->cmd_list);
- spin_unlock_irq(&sdev->list_lock);
+ if (shost->hostt->enable_cmd_list) {
+ spin_lock_irq(&sdev->list_lock);
+ list_add_tail(&cmd->list, &sdev->cmd_list);
+ spin_unlock_irq(&sdev->list_lock);
+ }
sg = (void *)cmd + sizeof(struct scsi_cmnd) + shost->hostt->cmd_size;
cmd->sdb.table.sgl = sg;
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index ba20347..ebef2eb 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -514,6 +514,9 @@ struct scsi_host_template {
/* temporary flag to disable blk-mq I/O path */
bool disable_blk_mq;
+
+ /* temporary flag to enable cmd_list per sdev */
+ bool enable_cmd_list;
};
/*
--
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