Re: [PATCH 3/3] High-res-timers part 3 (posix to hrposix) take 20

From: Jim Houston (
Date: Mon Dec 09 2002 - 20:55:47 EST

William Lee Irwin III wrote:
> On Mon, Dec 09, 2002 at 10:24:49AM -0500, Jim Houston wrote:
> > I got started on this before Ingo did his magic for hashing
> > pids. I prototyped in user space and did a quick hack to
> > make it work in the kernel. Yes, it uses a recursive approach
> > for the allocate and remove path. The recursion is limited
> > to only a few levels and the stack frame is tiny. For example
> > if there are 1000000 ids it will have 6 levels of recursion.
> I'm not Ingo but you'll figure it out.
> Recursion is unnecessary; the depths are bounded by BITS_PER_LONG
> divided by the log of the branch factor and looping over levels
> directly suffices.
> I started somewhat before the first for_each_task-* patches are
> dated on, which puts it sometime before May (obviously
> I spent time writing & testing before dropping it onto an ftp site).
> My original allocator(s) used a radix tree structured bitmap like this
> in order to provide hard constant time bounds, but statically-allocated
> them. Static allocation didn't fit in with larger pid space, though.
> Bill

Hi Bill,

Gee Bill, what can I say? I'm sorry I misattributed your work to Ingo.

I'm curious about the reaction to recursion. I use the obvious loop
for the lookup path, but the allocate and remove cases start getting
ugly as an iterative solution.

Jim Houston - Concurrent Computer Corp.
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