Re: [v8-users] Why does a combination of optimization flags(--always-opt --turbo) and code caching show bad performance?

2017-04-24 Thread Jin Chul Kim 
Thanks Jakob and Jochen!

Could you please answer the further questions?

1. Regarding code caching, does it keep native code or IR which will be 
translated into native code after loading?
2. May I know the limitations in code caching?

2017년 4월 21일 금요일 오후 11시 3분 2초 UTC+9, Jakob Kummerow 님의 말:
>
> As Jochen already said on chromium-dev, --always-opt does not make things 
> faster. This is expected. The purpose of the flag is to flush out certain 
> kinds of bugs when running tests, at the cost of a big slowdown.
>
> Code caching has limits. It cannot cache everything.
>
> The default configuration is what we believe gives the best performance in 
> general cases. There are no "secret" flags to make things faster.
>
> On Fri, Apr 21, 2017 at 9:27 AM, Jin Chul Kim  > wrote:
>
>> Hello,
>>
>> I am trying to reduce a execution time on general cases. My approach is a 
>> combination of two features: fully optimized code generation + code caching.
>> In my experiment, I figured out that code caching is very powerful. By 
>> the way, the execution time was significantly increased when I was using 
>> the following flags: --always-opt. I know turboFan was enabled on the 
>> recent V8 code. Here are my question.
>>
>> 1. As far as I know, code caching does not need code compilation to 
>> generate machine(native) code. Is that correct?
>>
>> I checked trace with --trace-opt. There were many lines for optimizing 
>> and compilation on code caching. why did them happen?
>>
>> [compiling method 0xed4b9e340c1 > (sfi = 0xed4b9e31ea1)> using TurboFan]
>> [optimizing 0xed4b9e340c1 > 0xed4b9e31ea1)> - took 0.081, 0.356, 0.039 ms]
>> [compiling method 0x3d3958a8f609 > 0xed4b9e41829)> using TurboFan]
>> [optimizing 0x3d3958a8f609 > 0xed4b9e41829)> - took 0.109, 0.560, 0.060 ms]
>> [compiling method 0x3d3958a93a81 > 0xed4b9e3d401)> using TurboFan]
>> [optimizing 0x3d3958a93a81 > 0xed4b9e3d401)> - took 0.028, 0.086, 0.011 ms]
>> ...
>>
>> 2. Do you explain why execution time is significantly increased on w/ 
>> opt. + w/ caching (examples 4) and 5) below)?
>>
>> If I was using the flag(--always-opt), the compiler may generates 
>> optimized or unoptimized code. Then, I think the second run should be same 
>> or better performance than the first run because it does not require 
>> compilation and just loads binary. Please see my experiment result as below:
>>
>> - baseline: w/o opt. + w/o caching
>> 1) 24.06 secs
>>
>> - w/o opt. + w/ caching
>> 2) 1st run(save native code): 24.35 secs
>> 3) 2nd run(load native code): 16.94 secs
>>
>> - w/ opt. + w/ caching
>> 4) 1st run(save native code): 75.12 secs
>> 5) 2nd run(load native code): 74.02 secs
>>
>> 3. How may I generate an optimal code to decrease an execution time on 
>> code caching?
>>
>> Many thanks,
>> Jinchul
>>
>> -- 
>> -- 
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>> http://groups.google.com/group/v8-users
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>
>

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Re: [v8-users] Why does a combination of optimization flags(--always-opt --turbo) and code caching show bad performance?

2017-04-21 Thread Jakob Kummerow 
As Jochen already said on chromium-dev, --always-opt does not make things
faster. This is expected. The purpose of the flag is to flush out certain
kinds of bugs when running tests, at the cost of a big slowdown.

Code caching has limits. It cannot cache everything.

The default configuration is what we believe gives the best performance in
general cases. There are no "secret" flags to make things faster.

On Fri, Apr 21, 2017 at 9:27 AM, Jin Chul Kim  wrote:

> Hello,
>
> I am trying to reduce a execution time on general cases. My approach is a
> combination of two features: fully optimized code generation + code caching.
> In my experiment, I figured out that code caching is very powerful. By the
> way, the execution time was significantly increased when I was using the
> following flags: --always-opt. I know turboFan was enabled on the recent V8
> code. Here are my question.
>
> 1. As far as I know, code caching does not need code compilation to
> generate machine(native) code. Is that correct?
>
> I checked trace with --trace-opt. There were many lines for optimizing and
> compilation on code caching. why did them happen?
>
> [compiling method 0xed4b9e340c1  = 0xed4b9e31ea1)> using TurboFan]
> [optimizing 0xed4b9e340c1  0xed4b9e31ea1)> - took 0.081, 0.356, 0.039 ms]
> [compiling method 0x3d3958a8f609  0xed4b9e41829)> using TurboFan]
> [optimizing 0x3d3958a8f609  0xed4b9e41829)> - took 0.109, 0.560, 0.060 ms]
> [compiling method 0x3d3958a93a81  0xed4b9e3d401)> using TurboFan]
> [optimizing 0x3d3958a93a81  0xed4b9e3d401)> - took 0.028, 0.086, 0.011 ms]
> ...
>
> 2. Do you explain why execution time is significantly increased on w/ opt.
> + w/ caching (examples 4) and 5) below)?
>
> If I was using the flag(--always-opt), the compiler may generates
> optimized or unoptimized code. Then, I think the second run should be same
> or better performance than the first run because it does not require
> compilation and just loads binary. Please see my experiment result as below:
>
> - baseline: w/o opt. + w/o caching
> 1) 24.06 secs
>
> - w/o opt. + w/ caching
> 2) 1st run(save native code): 24.35 secs
> 3) 2nd run(load native code): 16.94 secs
>
> - w/ opt. + w/ caching
> 4) 1st run(save native code): 75.12 secs
> 5) 2nd run(load native code): 74.02 secs
>
> 3. How may I generate an optimal code to decrease an execution time on
> code caching?
>
> Many thanks,
> Jinchul
>
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> v8-users@googlegroups.com
> http://groups.google.com/group/v8-users
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>

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