Bug #9584: RGenGC regression in CoW sharing

• Status: Closed
• Assignee: ko1 (Koichi Sasada)
• Target version: -
• ruby -v: -
• Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN, 2.1: UNKNOWN

[normalperson (Eric Wong)]

I just changed USE_RGENGC in ruby.h (and made r45224)
Using Nari-san's original test for bitmap marking GC:
https://github.com/authorNari/skkzipcode.git

rgengc enabled: (default)
PROCESS_CNT : 5
SHARED_AVE : 81644.0 kb
SHARED_TOTAL: 408220 kb
PRIV_AVE : 87692.0 kb
PRIV_TOTAL : 438460 kb
REQ/SEC : 0.003136

rgengc disabled:
PROCESS_CNT : 5
SHARED_AVE : 117307.2 kb
SHARED_TOTAL: 586536 kb
PRIV_AVE : 44453.6 kb
PRIV_TOTAL : 222268 kb
REQ/SEC : 0.002963

I started using bitmaps, but it seems there are some places where my code
is buggy. I haven't had more time to investigate, yet.
My work-in-progress is attached.

[ko1 (Koichi Sasada)]

Does it help for CoW friendly?

Basically, promoted bit is changed only for young objects.
To make young object, pages are marked dirty.

And also, I'm worry about WB performance.

[normalperson (Eric Wong)]

[e-mail] wrote:

Does it help for CoW friendly?

Basically, promoted bit is changed only for young objects.
To make young object, pages are marked dirty.

Yes, but look again at the SHARED_* numbers from nari's test
code. #define USE_RGENGC 0 shares more memory.

And also, I'm worry about WB performance.

I doubt it's much difference.
I haven't been able to fix my bitmap patch to test performance
(can't finish build, even). I suspect it's fake objects, I marked some with
FL_PERMANENT but maybe I missed some. If you have time, can you please
take a look?

[ko1 (Koichi Sasada)]

• ruby -v changed from ruby 2.2.0dev (2014-02-17 trunk 45028) [x86_64-linux] to -

(2014/03/01 19:01), Eric Wong wrote:

Yes, but look again at the SHARED_* numbers from nari's test
code. #define USE_RGENGC 0 shares more memory.

I doubt it caused from memory layout changing issue. RGenGC introduces
more memory pages for objects. This may prohibit to collect old object
closely.

Anyway, we need more survey about this issue.

And also, I'm worry about WB performance.
I doubt it's much difference.

Ordinally case, it doesn't affect.

I haven't been able to fix my bitmap patch to test performance
(can't finish build, even). I suspect it's fake objects, I marked some with
FL_PERMANENT but maybe I missed some. If you have time, can you please
take a look?

Sure. FL_PERMANENT is tricky :)

--
// SASADA Koichi at atdot dot net

[ko1 (Koichi Sasada)]

• Status changed from Open to Closed

we need to check it again.