From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: pavel@suse.cz (Pavel Machek)
Cc: linux-kernel@vger.kernel.org (kernel list)
Subject: Re: Reading from /dev/fb0 very slow?
Date: Sat, 2 Jun 2001 23:03:24 +0100 (BST) [thread overview]
Message-ID: <E156JUS-0002DC-00@the-village.bc.nu> (raw)
In-Reply-To: <20010602105249.A979@bug.ucw.cz> from "Pavel Machek" at Jun 02, 2001 10:52:49 AM
> I did some benchmarks, and my framebuffer is *way* faster when writing
> than when reading:
That is quite normal.
> 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]
Writes to a PCI device can be queued or posted. Reads from a PCI device for
obvious reasons have to stall the CPU until the data returns.
next prev parent reply other threads:[~2001-06-02 22:05 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-06-02 8:52 Pavel Machek
2001-06-02 21:42 ` Jeff Garzik
2001-06-02 22:03 ` Alan Cox [this message]
2001-06-02 22:46 ` Pavel Machek
2001-06-02 22:49 ` Alan Cox
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