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From "xiaoming gu" <xiaoming...@gmail.com>
Subject Re: a better selection heuristic for register allocation?
Date Mon, 22 Sep 2008 08:05:29 GMT
Thanks, Aleksey. The information is very helpful. -Xiaoming

On Mon, Sep 22, 2008 at 2:25 PM, Aleksey Shipilev <
aleksey.shipilev@gmail.com> wrote:

> Hi, Xiaoming!
>
> AFAIU, the real problem is the compilation time when CG is enabled.
> You might experiment though: take server.emconf, walk around disabling
> BP in SD2_OPT (i.e. set the threshold to 0) and see the difference.
> There's also an interesting question, what methods would go to SD2_OPT
> pipeline, but there should be only hot methods. The hottness is
> defined by profiler constraints there.
>
> I'm recalling that some workloads like OC4J fail (fatal exceptions in
> WebMaker) when threshold is less than 2500 -- I believe that was the
> reason of having 10000 in server_aggressive.
>
> Thanks,
> Aleksey.
>
>
> On 9/20/08, xiaoming gu <xiaoming.gu@gmail.com> wrote:
> > Hi, all. I did some study of register allocation these days. In current
> > version, there are two kinds of register allocation - bin-packing (BP)
> and
> > coloring-graph (CG). In client modes (client and opt), only BP is used.
> In
> > server modes (server, server_aggressive and server_static), BP and CG are
> > two choices for the being compiled function. If the number of operands in
> > the function is less than a threshold, CG is selected. Otherwise, BP is
> > selected. The default value for this threshold is 2000 and in
> > server_aggressive it's set to 10000.
> >
> > My question is that is it better to make the selection heuristic for
> BP/CG
> > more meaningful? An intuitive is to use CG for hot functions. What's your
> > opinions? Thanks.
> >
> > Xiaoming
> >
>

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