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Re: Patch: Bitmap marking
- To: Bryce McKinlay <bryce at albatross dot co dot nz>
- Subject: Re: Patch: Bitmap marking
- From: Jeff Sturm <jeff dot sturm at appnet dot com>
- Date: Thu, 31 Aug 2000 17:02:21 -0400
- CC: java-patches at sourceware dot cygnus dot com
- Organization: AppNet Inc.
- References: <398FC919.252A4368@albatross.co.nz>
Bryce McKinlay wrote:
> I've cleaned up, tested, and written ChangeLog entries for the Boehm
> GC bitmap descriptor marking patch. This is basically the same as Hans'
> version of the patch, but with formatting fixes, and a fix for an
> off-by-one error in the vtable copying code in _Jv_FindArrayClass. The
> patch is working well with the current tree.
I tested this patch on a few different systems. It looks good, with one
mysterious exception: on Alpha it caused a strange abort() in _Jv_ThreadWait.
Although it may not be related to the bitmap marking, I've never seen that
happen, so I'll continue to investigate.
I also tried GCBench
<uri:http://www.hpl.hp.com/personal/Hans_Boehm/gc/gc_bench.html> to get an idea
of the improvements with bitmap marking. I tested the original marking code
along with pure conservative marking and the new bitmap marking on three
development machines I have:
| original | conservative | bitmap marking
i686-pc-linux-gnu | 16.9s | 15.1s (-11%) | 12.8s (-25%)
sparc-sun-solaris | 43.4 | 33.1 (-24%) | 33.3 (-24%)
alpha-unknown-linux-gnu | 39.5 | 26.4 (-34%) | 28.5 (-28%)
On x86 bitmap marking seems to be a clear win, but on these two RISC machines it
is actually slower than simple conservative marking. Not quite what I expected.