[PATCH 09/11] target_core_user: add backend plug/unplug callouts
From: Mike Christie <michael.christie@oracle.com>
Date: 2021-02-04 11:38:07
Also in:
target-devel
Subsystem:
scsi target core user driver, scsi target subsystem, the rest · Maintainers:
Bodo Stroesser, "Martin K. Petersen", Linus Torvalds
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 and fio jobs this patch can increase IOPs by only around 5% because we hit other issues like the big per tcmu device mutex. Bodo, because the improvement is so small I'm not sure if we want this patch. I was thinking when you fix those other issues you've been working on then it might be more useful. Signed-off-by: Mike Christie <michael.christie@oracle.com> --- drivers/target/target_core_user.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-)
diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index a5991df23581..d67be2f959b9 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c@@ -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 +961,26 @@ 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); + + uio_event_notify(&udev->uio_info); + clear_bit(TCM_DEV_BIT_PLUGGED, &udev->flags); +} + +static struct se_dev_plug *tcmu_plug_device(struct se_cmd *se_cmd) +{ + struct se_device *se_dev = se_cmd->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 +1108,8 @@ 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;
@@ -2840,6 +2862,8 @@ 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,
--
2.25.1