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scsi: target: tcmu: Add backend plug/unplug callouts

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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: Bodo Stroesser <bostroesser@gmail.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Mike Christie 2021-02-27 11:00:04 -06:00 committed by Martin K. Petersen
parent 415ccd9811
commit 6888da8179
1 changed files with 25 additions and 2 deletions
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27
drivers/target/target_core_user.c
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@ -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
@ -1086,8 +1107,8 @@ 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? */
uio_event_notify(&udev->uio_info);
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,