[Fwd: low-latency patches]

[J Sloan]

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Date: Fri, 05 Oct 2001 23:51:55 -0700
From: J Sloan <[e-mail]>
Organization: J S Concepts
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To: Bob McElrath <[e-mail]>
Subject: Re: low-latency patches
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Bob McElrath wrote:

> It seems there are two low-latency projects out there.  The one by Robert Love:
>     http://tech9.net/rml/linux/
> and the original one:
>     http://www.uow.edu.au/~andrewm/linux/schedlat.html
>
> Correct me if I'm wrong, but the former uses spinlocks to know when it can
> preempt the kernel, and the latter just tries to reduce latency by adding
> (un)conditional_schedule and placing it at key places in the kernel?
>
> My questions are:
> 1) Which of these two projects has better latency performance?  Has anyone
>     benchmarked them against each other?
> 2) Will either of these ever be merged into Linus' kernel (2.5?)
> 3) Is there a possibility that either of these will make it to non-x86
>     platforms?  (for me: alpha)  The second patch looks like it would
>     straightforwardly work on any arch, but the config.in for it is only in
>     arch/i386.  Robert Love's patches would need some arch-specific asm...

In my experience with them, the Andrew Morton patches
provide a "smoother" interactive feel, great for things like
online gaming (quake 3 arena, etc), however the Robert
Love patches are simpler, seem less intrusive, and I've
had better luck with them on smp, highmem boxes.

(just IMHO) I like Andrew's patches on (up) workstations,
and Robert's on (smp) servers, with some grey area of
overlap -

I'm hardly the person to say, but the rml patches would
seem more likely to go in sooner, if at all.  I'd love to see
both remain an option.

cu

jjs

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