From: Linus Torvalds Date: Tue, 22 Mar 2011 23:17:32 +0000 (-0700) Subject: tty: stop using "delayed_work" in the tty layer X-Git-Tag: v2.6.39-rc1~383 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f23eb2b2b28547fc70df82dd5049eb39bec5ba12;p=pandora-kernel.git 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 Acked-by: Greg KH Acked-by: Alan Cox Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed