Commit 6888da81 authored by Mike Christie's avatar Mike Christie Committed by Martin K. Petersen
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scsi: target: tcmu: Add backend plug/unplug callouts 

This patch adds plug/unplug callouts for tcmu, so we can avoid the number
of times we switch to userspace. Using this driver with tcm_loop is a
common config, and dependng on the nr_hw_queues (nr_hw_queues=1 performs
much better) and fio jobs (lower num jobs around 4) this patch can increase
IOPS by only around 5-10% because we hit other issues like the big per tcmu
device mutex.

Link: https://lore.kernel.org/r/20210227170006.5077-24-michael.christie@oracle.com


Reviewed-by: default avatarBodo Stroesser <bostroesser@gmail.com>
Signed-off-by: default avatarMike Christie <michael.christie@oracle.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 415ccd98

drivers/target/target_core_user.c

+25 −2
Original line number Diff line number Diff line
@@ -111,6 +111,7 @@ struct tcmu_dev { 
	struct kref kref;



	struct se_device se_dev;

	struct se_dev_plug se_plug;



	char *name;

	struct se_hba *hba;
@@ -119,6 +120,7 @@ struct tcmu_dev { 
#define TCMU_DEV_BIT_BROKEN 1

#define TCMU_DEV_BIT_BLOCKED 2

#define TCMU_DEV_BIT_TMR_NOTIFY 3

#define TCM_DEV_BIT_PLUGGED 4

	unsigned long flags;



	struct uio_info uio_info;
@@ -959,6 +961,25 @@ static uint32_t ring_insert_padding(struct tcmu_dev *udev, size_t cmd_size) 
	return cmd_head;

}



static void tcmu_unplug_device(struct se_dev_plug *se_plug)

{

	struct se_device *se_dev = se_plug->se_dev;

	struct tcmu_dev *udev = TCMU_DEV(se_dev);



	clear_bit(TCM_DEV_BIT_PLUGGED, &udev->flags);

	uio_event_notify(&udev->uio_info);

}



static struct se_dev_plug *tcmu_plug_device(struct se_device *se_dev)

{

	struct tcmu_dev *udev = TCMU_DEV(se_dev);



	if (!test_and_set_bit(TCM_DEV_BIT_PLUGGED, &udev->flags))

		return &udev->se_plug;



	return NULL;

}



/**

 * queue_cmd_ring - queue cmd to ring or internally

 * @tcmu_cmd: cmd to queue
@@ -1086,7 +1107,7 @@ static int queue_cmd_ring(struct tcmu_cmd *tcmu_cmd, sense_reason_t *scsi_err) 


	list_add_tail(&tcmu_cmd->queue_entry, &udev->inflight_queue);



	/* TODO: only if FLUSH and FUA? */

	if (!test_bit(TCM_DEV_BIT_PLUGGED, &udev->flags))

		uio_event_notify(&udev->uio_info);



	return 0;
@@ -2863,6 +2884,8 @@ static struct target_backend_ops tcmu_ops = { 
	.configure_device	= tcmu_configure_device,

	.destroy_device		= tcmu_destroy_device,

	.free_device		= tcmu_free_device,

	.unplug_device		= tcmu_unplug_device,

	.plug_device		= tcmu_plug_device,

	.parse_cdb		= tcmu_parse_cdb,

	.tmr_notify		= tcmu_tmr_notify,

	.set_configfs_dev_params = tcmu_set_configfs_dev_params,