O_SYNC patch -> slow fb memory access
Egbert, Debian folks:
After the release of XFree86 4.3.0, (AFAIK) Egbert Eich commited a patch
which set the O_SYNC flag when opening /dev/mem for framebuffer memory
access.
This caused memory access to the framebuffer area to become terribly
slow on some machines. Among these types of machines are practically all
SiS based ones using a shared memory area for framebuffer memory.
It seems the Debian folks have included this patch in their experimental
pre1 prerelease, as I experience severe performance regressions compared
to plain 4.3 from XFree.org.
Egbert: What exactly did that patch, what file is affected, and when was
this reverted (I know it's not in current HEAD)?
Debian packagers: In case you know what I am talking about, please
remove this patch from upcoming releases. It's consequences are quite
inconvenient: Xv, depending on fast memory access, takes up to 30% CPU
time, while this is about 4% without that O_SYNC stuff.
Thomas
--
Thomas Winischhofer
Vienna/Austria
thomas AT winischhofer DOT net http://www.winischhofer.net/
twini AT xfree86 DOT org
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