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Re: QtHandles and performance
From: |
John W. Eaton |
Subject: |
Re: QtHandles and performance |
Date: |
Fri, 10 Jan 2014 16:49:16 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131005 Icedove/17.0.9 |
On 01/09/2014 04:37 PM, John W. Eaton wrote:
On 01/09/2014 04:30 PM, Rik wrote:
On 01/09/2014 12:06 PM, address@hidden wrote:
Do we need to re-measure the performance penalty before we can make an
informed decision, or are we confident in the 10% number?
Measuring again is probably a good idea. I compiled with optimization
enabled (default -O2 for GCC) and timed running the test suite to compare.
OK, I did that test again and this is what I see (default -g -O2
compiler options for both cases):
without atomic refcount (current default):
make[1]: Leaving directory `/scratch/jwe/build/octave-opt/test'
401.45user 49.45system 7:50.31elapsed 95%CPU (0avgtext+0avgdata
415228maxresident)k
153352inputs+20904outputs (172major+16480393minor)pagefaults 0swaps
with atomic refcount:
make[1]: Leaving directory `/scratch/jwe/build/octave-opt-atomic/test'
405.32user 49.07system 7:51.65elapsed 96%CPU (0avgtext+0avgdata
415348maxresident)k
85768inputs+20920outputs (54major+16128734minor)pagefaults 0swaps
That's about, like, no difference. Hmm. And yes, octave-opt/config.h
has
/* #undef USE_ATOMIC_REFCOUNT */
and octave-opt-atomic/config.h has
#define USE_ATOMIC_REFCOUNT 1
Well, that's not the result I was expecting. So I guess there's no
reason to NOT use atomic refcount. I ran the test with GCC 4.8.2 on an
x86_64 system. Maybe it was worse with earlier versions of GCC? I
guess I could try that just to see if I can confirm what I remember as
the previous result. Or we could also look up the previous discussion
in the mailing list archives.
jwe