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Re: [rfc] Frame based register cache / frame->unwind
- From: Daniel Jacobowitz <drow at mvista dot com>
- To: gdb at sources dot redhat dot com
- Date: Sun, 14 Apr 2002 21:49:16 -0400
- Subject: Re: [rfc] Frame based register cache / frame->unwind
- References: <3CB9ED82.email@example.com>
On Sun, Apr 14, 2002 at 04:58:42PM -0400, Andrew Cagney wrote:
> To pull together several apparently random threads. The attached is a
> work in progress to add a frame based register cache to GDB. It appears
> to work - NetBSD/PPC shows no regressions.
> Performance is hard to quantify(1) but looks positive. Using a native
> GDB (not typical for me :-) it appears that each frame is ~2% slower to
> create (``(gdb) up''). Once created, the frame is ~20-25% faster
> (``(gdb) info registers'').
You might want to try timing the testsuite with and without this patch
(using /usr/bin/time et al., to get real/user/sys times) and see what
changes. It'll probably be negligible, but you never know.
> I'm not too worried about the apparent 2% overhead per frame create
> though. With the patch applied, the code ends up maintaining both this
> new cache and the old ->saved_regs table. Rewriting a target to just
> use the ->unwind_cache, should, I think, claw back the 2% and then some
> - less need to go out to the target.
> There are two parts to the change and I'll describe each in turn. The
> final patch will likely be committed as two parts.
Looks wonderful to me!
Daniel Jacobowitz Carnegie Mellon University
MontaVista Software Debian GNU/Linux Developer