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Small performance optimization: wake up IO/processing threads in LIFO order.

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git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@928 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This commit is contained in:
Vladislav Bolkhovitin
2009-06-30 16:13:48 +00:00
parent 700eb30c9c
commit fb0256ba8a
4 changed files with 23 additions and 4 deletions
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4
iscsi-scst/kernel/nthread.c
View File

@@ -974,7 +974,7 @@ int istrd(void *arg)
init_waitqueue_entry(&wait, current);
if (!test_rd_list()) {
add_wait_queue_exclusive(&iscsi_rd_waitQ, &wait);
add_wait_queue_exclusive_head(&iscsi_rd_waitQ, &wait);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
if (test_rd_list())
@@ -1662,7 +1662,7 @@ int istwr(void *arg)
init_waitqueue_entry(&wait, current);
if (!test_wr_list()) {
add_wait_queue_exclusive(&iscsi_wr_waitQ, &wait);
add_wait_queue_exclusive_head(&iscsi_wr_waitQ, &wait);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
if (test_wr_list())

17
scst/include/scst.h
View File

@@ -26,6 +26,7 @@
#include <linux/blkdev.h>
#include <linux/interrupt.h>
#include <linux/proc_fs.h>
#include <linux/wait.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
@@ -3075,4 +3076,20 @@ int scst_tape_generic_dev_done(struct scst_cmd *cmd,
*/
int scst_obtain_device_parameters(struct scst_device *dev);
/*
* Has to be put here open coded, because Linux doesn't have equivalent, which
* allows exclusive wake ups of threads in LIFO order. We need it to let (yet)
* unneeded threads sleep and not pollute CPU cache by their stacks.
*/
static inline void add_wait_queue_exclusive_head(wait_queue_head_t *q,
wait_queue_t *wait)
{
unsigned long flags;
wait->flags |= WQ_FLAG_EXCLUSIVE;
spin_lock_irqsave(&q->lock, flags);
__add_wait_queue(q, wait);
spin_unlock_irqrestore(&q->lock, flags);
}
#endif /* __SCST_H */

3
scst/src/dev_handlers/scst_user.c
View File

@@ -1745,7 +1745,8 @@ static int dev_user_get_next_cmd(struct scst_user_dev *dev,
while (1) {
if (!test_cmd_lists(dev)) {
add_wait_queue_exclusive(&dev->cmd_lists.cmd_list_waitQ,
add_wait_queue_exclusive_head(
&dev->cmd_lists.cmd_list_waitQ,
&wait);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);

3
scst/src/scst_targ.c
View File

@@ -3735,7 +3735,8 @@ int scst_cmd_thread(void *arg)
init_waitqueue_entry(&wait, current);
if (!test_cmd_lists(p_cmd_lists)) {
add_wait_queue_exclusive(&p_cmd_lists->cmd_list_waitQ,
add_wait_queue_exclusive_head(
&p_cmd_lists->cmd_list_waitQ,
&wait);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);