From: Jeff Garzik <jgarzik@mandrakesoft.com>
To: Pavel Machek <pavel@suse.cz>
Cc: kernel list <linux-kernel@vger.kernel.org>
Subject: Re: Reading from /dev/fb0 very slow?
Date: Sat, 02 Jun 2001 17:42:27 -0400 [thread overview]
Message-ID: <3B195DC3.EE919B3F@mandrakesoft.com> (raw)
In-Reply-To: <20010602105249.A979@bug.ucw.cz>
Pavel Machek wrote:
>
> 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]
Do you have write combining enabled?
--
Jeff Garzik | Echelon words of the day, from The Register:
Building 1024 | FRU Lebed HALO Spetznaz Al Amn al-Askari Glock 26
MandrakeSoft | Steak Knife Kill the President anarchy echelon
| nuclear assassinate Roswell Waco World Trade Center
next prev parent reply other threads:[~2001-06-02 21:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-06-02 8:52 Reading from /dev/fb0 very slow? Pavel Machek
2001-06-02 21:42 ` Jeff Garzik [this message]
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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