From 4d2300ccffd22d1d0213b6a8e4d685eb6ca069c0 Mon Sep 17 00:00:00 2001 From: Nicholas Bellinger Date: Wed, 30 Nov 2011 18:18:33 -0800 Subject: [PATCH] target: Remove extra se_device->execute_task_lock access in fast path This patch makes __transport_execute_tasks() perform the addition of tasks to dev->execute_task_list via __transport_add_tasks_from_cmd() while holding dev->execute_task_lock during normal I/O fast path submission. It effectively removes the unnecessary re-acquire of dev->execute_task_lock during transport_execute_tasks() -> transport_add_tasks_from_cmd() ahead of calling __transport_execute_tasks() to queue tasks for the passed *se_cmd descriptor. (v2: Re-add goto check_depth usage for multi-task submission for now..) Cc: Christoph Hellwig Cc: Roland Dreier Cc: Joern Engel Signed-off-by: Nicholas Bellinger --- drivers/target/target_core_transport.c | 40 +++++++++++++++----------- include/target/target_core_base.h | 1 - 2 files changed, 24 insertions(+), 17 deletions(-) diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c index 7c2def7e2593..46e25118ab25 100644 --- a/drivers/target/target_core_transport.c +++ b/drivers/target/target_core_transport.c @@ -68,7 +68,7 @@ struct kmem_cache *t10_alua_tg_pt_gp_mem_cache; static int transport_generic_write_pending(struct se_cmd *); static int transport_processing_thread(void *param); -static int __transport_execute_tasks(struct se_device *dev); +static int __transport_execute_tasks(struct se_device *dev, struct se_cmd *); static void transport_complete_task_attr(struct se_cmd *cmd); static void transport_handle_queue_full(struct se_cmd *cmd, struct se_device *dev); @@ -851,13 +851,11 @@ static void transport_add_tasks_to_state_queue(struct se_cmd *cmd) spin_unlock_irqrestore(&cmd->t_state_lock, flags); } -static void transport_add_tasks_from_cmd(struct se_cmd *cmd) +static void __transport_add_tasks_from_cmd(struct se_cmd *cmd) { struct se_device *dev = cmd->se_dev; struct se_task *task, *task_prev = NULL; - unsigned long flags; - spin_lock_irqsave(&dev->execute_task_lock, flags); list_for_each_entry(task, &cmd->t_task_list, t_list) { if (!list_empty(&task->t_execute_list)) continue; @@ -868,6 +866,15 @@ static void transport_add_tasks_from_cmd(struct se_cmd *cmd) __transport_add_task_to_execute_queue(task, task_prev, dev); task_prev = task; } +} + +static void transport_add_tasks_from_cmd(struct se_cmd *cmd) +{ + unsigned long flags; + struct se_device *dev = cmd->se_dev; + + spin_lock_irqsave(&dev->execute_task_lock, flags); + __transport_add_tasks_from_cmd(cmd); spin_unlock_irqrestore(&dev->execute_task_lock, flags); } @@ -2075,19 +2082,16 @@ static int transport_execute_tasks(struct se_cmd *cmd) if (!add_tasks) goto execute_tasks; /* - * This calls transport_add_tasks_from_cmd() to handle - * HEAD_OF_QUEUE ordering for SAM Task Attribute emulation - * (if enabled) in __transport_add_task_to_execute_queue() and - * transport_add_task_check_sam_attr(). + * __transport_execute_tasks() -> __transport_add_tasks_from_cmd() + * adds associated se_tasks while holding dev->execute_task_lock + * before I/O dispath to avoid a double spinlock access. */ - transport_add_tasks_from_cmd(cmd); + __transport_execute_tasks(se_dev, cmd); + return 0; } - /* - * Kick the execution queue for the cmd associated struct se_device - * storage object. - */ + execute_tasks: - __transport_execute_tasks(se_dev); + __transport_execute_tasks(se_dev, NULL); return 0; } @@ -2097,7 +2101,7 @@ execute_tasks: * * Called from transport_processing_thread() */ -static int __transport_execute_tasks(struct se_device *dev) +static int __transport_execute_tasks(struct se_device *dev, struct se_cmd *new_cmd) { int error; struct se_cmd *cmd = NULL; @@ -2106,6 +2110,9 @@ static int __transport_execute_tasks(struct se_device *dev) check_depth: spin_lock_irq(&dev->execute_task_lock); + if (new_cmd != NULL) + __transport_add_tasks_from_cmd(new_cmd); + if (list_empty(&dev->execute_task_list)) { spin_unlock_irq(&dev->execute_task_lock); return 0; @@ -2139,6 +2146,7 @@ check_depth: transport_generic_request_failure(cmd); } + new_cmd = NULL; goto check_depth; return 0; @@ -4647,7 +4655,7 @@ static int transport_processing_thread(void *param) goto out; get_cmd: - __transport_execute_tasks(dev); + __transport_execute_tasks(dev, NULL); cmd = transport_get_cmd_from_queue(&dev->dev_queue_obj); if (!cmd) diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h index cd4caf3a598f..a74cb2be74de 100644 --- a/include/target/target_core_base.h +++ b/include/target/target_core_base.h @@ -781,7 +781,6 @@ struct se_device { u32 dev_port_count; /* See transport_device_status_table */ u32 dev_status; - u32 dev_tcq_window_closed; /* Physical device queue depth */ u32 queue_depth; /* Used for SPC-2 reservations enforce of ISIDs */ -- 2.20.1