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Date: Thu, 6 Mar 2003 18:17:11 +0100 (CET)
From: Ingo Molnar <mingo@elte.hu>
Reply-To: Ingo Molnar <mingo@elte.hu>
To: Jeff Garzik <jgarzik@pobox.com>
Cc: Linus Torvalds <torvalds@transmeta.com>, Andrew Morton <akpm@digeo.com>,
       Robert Love <rml@tech9.net>, <linux-kernel@vger.kernel.org>
Subject: Re: [patch] "HT scheduler", sched-2.5.63-B3
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On Thu, 6 Mar 2003, Jeff Garzik wrote:

> Pardon the suggestion of a dumb hueristic, feel free to ignore me:  
> would it work to run-first processes that have modified their iopl()  
> level?  i.e. "if you access hardware directly, we'll treat you specially
> in the scheduler"?

we did this in the Red Hat kernel, just as a quick hack to boost X without
having to modify X (bleh). While it worked very well in practice, it's a
really bad idea from an interface design POV, because it singles out X
mostly based on a random characteristics of X, but leaves out some other
tasks that are 'suffering' from not being recognized as interactive, but
still having a user watching them (and expecting keypresses to react
fast): games, xine, XMMS, etc.

> An alternative is to encourage distros to set some sort of flag for
> processes like the X server, when it is run.  This sounds suspiciously
> like the existing "renice X server" hack, but it could be something like
> changing the X server from SCHED_OTHER to SCHED_HW_ACCESS instead.

yes, an ELF flag might work, or my suggestion to allow applications to
increase their priority (up until a certain degree).

	Ingo

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