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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2011-03-22 16:17:32 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-03-22 16:17:32 -0700 |
| commit | f23eb2b2b28547fc70df82dd5049eb39bec5ba12 (patch) | |
| tree | 144dce462b34d8a232a06f766786ebfb0235fa87 /include/linux/tty.h | |
| parent | f741a79e982cf56d7584435bad663553ffe6715f (diff) | |
| download | lwn-f23eb2b2b28547fc70df82dd5049eb39bec5ba12.tar.gz lwn-f23eb2b2b28547fc70df82dd5049eb39bec5ba12.zip | |
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/tty.h')
| -rw-r--r-- | include/linux/tty.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h index 4e53d4641b38..9f469c700550 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 */ |