v8 try catch performance...

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v8 try catch performance... billywhizz 2/18/11 9:19 PM
i was doing some parser benchmarks today and noticed that i took a big
(20%) performance hit on my tests when i wrapped my parse function in
a try catch. i did some googling and came across this:

http://code.google.com/p/v8/issues/detail?id=1065

"Because of the with or try/catch we allocate all the parameters and
locals in the heap."

just thought people should be aware of it and hopefully it's something
that can be addressed...
Re: v8 try catch performance... tjholowaychuk 2/19/11 10:18 AM
yikes :s
Re: [node-dev] Re: v8 try catch performance... Zachary Scott 2/19/11 9:19 PM
Hi Billy,
Think you can share your tests?

--
Zachary Scott

Re: v8 try catch performance... billywhizz 2/20/11 2:22 PM
Zachary, i don't have an easy to post code but i was testing my
fastcgi parser here: https://github.com/billywhizz/node-fastcgi-parser.

if you clone it and check out master you should be able to reproduce
by running

node benchmark/createtestfiles.js 1000000

to create the test files and

node benchmark/speed-fcgi.js out 16
node benchmark/speed-fcgi.js in 16

to run the performance tests.

run the same tests again after putting a try/catch around the
Parser.execute method in lib/parser.js and you should see a big
performance hit. on my setup (fedora 12/64 on Core 2 Quad Q8200  @
2.33GHz) i get the following numbers:

without try/catch:
Rec:153021, Time: 1002, Rec/Sec: 152716, MBit/Sec: 152
Rec:147706, Time: 1000, Rec/Sec: 147706, MBit/Sec: 147
Rec:149207, Time: 1000, Rec/Sec: 149207, MBit/Sec: 149
Rec:151146, Time: 1001, Rec/Sec: 150995, MBit/Sec: 150
Rec:150270, Time: 999, Rec/Sec: 150420, MBit/Sec: 150
Rec:152896, Time: 1000, Rec/Sec: 152896, MBit/Sec: 152

with try/catch:
Rec:125318, Time: 1003, Rec/Sec: 124943, MBit/Sec: 124
Rec:121817, Time: 1000, Rec/Sec: 121817, MBit/Sec: 121
Rec:124256, Time: 1000, Rec/Sec: 124256, MBit/Sec: 124
Rec:124443, Time: 1000, Rec/Sec: 124443, MBit/Sec: 124
Rec:124319, Time: 999, Rec/Sec: 124443, MBit/Sec: 124
Rec:123943, Time: 1000, Rec/Sec: 123943, MBit/Sec: 123
Rec:124193, Time: 1000, Rec/Sec: 124193, MBit/Sec: 124
Rec:124693, Time: 1000, Rec/Sec: 124693, MBit/Sec: 124

i'll see if i can reduce the test to something gist-able...

On Feb 20, 5:19 am, Zachary Scott <zachary.s.sc...@gmail.com> wrote:
> Hi Billy,
> Think you can share your tests?
>
Re: v8 try catch performance... billywhizz 2/20/11 2:39 PM
right, i've stuck a gist up here: https://gist.github.com/836387 which
shows the issue quite well.

the upshot of it seems to be that if you have a function that has
performance critical code in it (particularly if it's allocating a lot
of variables), then don't use a try/catch inside the function and
catch the errors from outside the function instead.
Re: [node-dev] Re: v8 try catch performance... Zachary Scott 2/22/11 7:29 AM
Interesting... thanks for sharing!
Will try to avoid this in the future :)
Re: [node-dev] Re: v8 try catch performance... Marco Rogers 2/23/11 9:18 AM
Wow, that sucks.  Very good to know though.

:Marco
Re: [node-dev] Re: v8 try catch performance... Mikeal Rogers 2/23/11 1:03 PM
indeed, it would be nice to consolidate some of the work that has been done trying to understand v8 performance as we continue to find things are unexplainably fast and things that are randomly kind of slow :)
Re: v8 try catch performance... billywhizz 2/23/11 3:51 PM
yes. would be nice to have a best practices page on the wiki along
with a bunch of performance tests which we can monitor with each new
release of v8... maybe we should create as a separate repo for now and
we can add it to the main repo at some stage if there is agreement to
do so...?
Re: [node-dev] Re: v8 try catch performance... Zachary Scott 2/23/11 5:43 PM
+1 for node/v8 best practices doc
Re: [node-dev] Re: v8 try catch performance... Marco Rogers 2/24/11 10:18 AM

Boom, done.

https://github.com/joyent/node/wiki/Best-practices-and-gotchas-with-v8

Not sure if this is the best format, but it's better than nothing.  Check out the jsperf test I set up.  Other js engines don't have this overhead. All test runs have pretty uniform performance. But they are also significantly slower than the v8 control case.

:Marco
Re: [node-dev] Re: v8 try catch performance... Marco Rogers 2/25/11 11:38 AM
Holy crap, check out the jump in performance between firefox 4 beta11 and beta12 (attached).  Might be an outlier because only 1 test on beta12, but still.




Re: [node-dev] Re: v8 try catch performance... bradley.meck 2/25/11 12:45 PM
Were those from the same machine? Sometimes the speed is misleading, the % diff between tests is what is actually telling on jsperf.
Re: [node-dev] Re: v8 try catch performance... Marco Rogers 2/25/11 1:24 PM
Good point.  I'm sure it shouldn't be taken at face value.  But the performance on FF 4 has been increasing steadily.  v8 and node.js notwithstanding, I still prefer Firefox to Chrome for a few key reasons.  I want them to get back in the game and be competitive.

:Marco


On Fri, Feb 25, 2011 at 3:45 PM, bradley.meck <bradle...@gmail.com> wrote:
Were those from the same machine? Sometimes the speed is misleading, the % diff between tests is what is actually telling on jsperf.



--
Marco Rogers
marco....@gmail.com

Life is ten percent what happens to you and ninety percent how you respond to it.
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