From: Pavel Machek <pavel@suse.cz>
To: kernel list <linux-kernel@vger.kernel.org>
Subject: Reading from /dev/fb0 very slow?
Date: Sat, 2 Jun 2001 10:52:49 +0200 [thread overview]
Message-ID: <20010602105249.A979@bug.ucw.cz> (raw)
Hi!
I did some benchmarks, and my framebuffer is *way* faster when writing
than when reading:
root@bug:/home/pavel# time cat /tmp/test > /dev/fb0
0.01user 0.08system 0.09 (0m0.097s) elapsed 93.13%CPU
root@bug:/home/pavel# time cat /dev/fb0 > /dev/null
0.00user 0.62system 0.62 (0m0.620s) elapsed 99.93%CPU
root@bug:/home/pavel#
That is 6 times slower! This is also very visible in X, where moving
regions is expensive, while just drawing regions is fast. For example
gnome-terminal is *way* faster *with* transparent background option.
Any idea why such assymetry? [This is toshiba 4030cdt with vesafb and
2.4.5]
Pavel
--
I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care."
Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org
next reply other threads:[~2001-06-02 21:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-06-02 8:52 Pavel Machek [this message]
2001-06-02 21:42 ` Reading from /dev/fb0 very slow? Jeff Garzik
2001-06-02 22:03 ` Alan Cox
2001-06-02 22:46 ` Pavel Machek
2001-06-02 22:49 ` Alan Cox
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