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authorLinus Torvalds <torvalds@linux-foundation.org>2011-03-22 16:17:32 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-03-22 16:17:32 -0700
commitf23eb2b2b28547fc70df82dd5049eb39bec5ba12 (patch)
tree144dce462b34d8a232a06f766786ebfb0235fa87 /include/linux
parentf741a79e982cf56d7584435bad663553ffe6715f (diff)
tty: stop using "delayed_work" in the tty layer
Using delayed-work for tty flip buffers ends up causing us to wait for the next tick to complete some actions. That's usually not all that noticeable, but for certain latency-critical workloads it ends up being totally unacceptable. As an extreme case of this, passing a token back-and-forth over a pty will take two ticks per iteration, so even just a thousand iterations will take 8 seconds assuming a common 250Hz configuration. Avoiding the whole delayed work issue brings that ping-pong test-case down to 0.009s on my machine. In more practical terms, this latency has been a performance problem for things like dive computer simulators (simulating the serial interface using the ptys) and for other environments (Alan mentions a CP/M emulator). Reported-by: Jef Driesen <jefdriesen@telenet.be> Acked-by: Greg KH <gregkh@suse.de> Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/kbd_kern.h2
-rw-r--r--include/linux/tty.h2
2 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/kbd_kern.h b/include/linux/kbd_kern.h
index 4b0761cc7dd..ec2d17bc1f1 100644
--- a/include/linux/kbd_kern.h
+++ b/include/linux/kbd_kern.h
@@ -159,7 +159,7 @@ static inline void con_schedule_flip(struct tty_struct *t)
if (t->buf.tail != NULL)
t->buf.tail->commit = t->buf.tail->used;
spin_unlock_irqrestore(&t->buf.lock, flags);
- schedule_delayed_work(&t->buf.work, 0);
+ schedule_work(&t->buf.work);
}
#endif
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 4e53d4641b3..9f469c70055 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -82,7 +82,7 @@ struct tty_buffer {
struct tty_bufhead {
- struct delayed_work work;
+ struct work_struct work;
spinlock_t lock;
struct tty_buffer *head; /* Queue head */
struct tty_buffer *tail; /* Active buffer */