Re: [v8-users] Property access time in JavaScript programs

2015-09-30 Thread dmonji 
What does the percentage mentioned in brackets refer to? Does ic miss 
(24.3%) means 24.3 % of total execution time was spent on inline cache 
misses? But
surprisingly these percentages do not add to 100%. 

Also, is it possible to see JITed code, where I can see how the code looks 
with inline caches? I am aware of --trace_ic which gives out the 
information about 
LOADIC and STOREIC. But I want to see how the original code looks after 
introducing code for inline caching.

On Friday, 18 September 2015 18:44:43 UTC+5:30, Jakob Kummerow wrote:
>
> I don't think it's possible to measure property access times directly. One 
> reason is that a single property access is much, much faster than getting a 
> timestamp from the operating system.
>
> So your best bet is probably to measure it indirectly: take a long-running 
> loop, add a single property access in such a way that (1) it can't be 
> optimized away by the compiler and (2) it doesn't introduce additional 
> operations, which isn't easy to achieve at the same time, and measure how 
> much longer the overall loop takes than it did before.
>
> Of course that would be a very artificial micro-benchmark, and would only 
> measure one very specific situation. In the general case, property accesses 
> can take *very* different amounts of time, though: in the best case, 
> they're a single machine instruction; in the worst case, they're thousands 
> of machine instructions. It all depends on so many things...
>
> I can't think of a way to take an existing program and accurately measure 
> what fraction of its running time is spent on property accesses.
>
> On Fri, Sep 18, 2015 at 1:13 PM, dmonji  > wrote:
>
>> Is there any way to measure it? 
>>
>> I tried to instrument the JavaScript code, and summed up the time between 
>> "before access" and "after access". But I am not very sure if this is
>> the right way to measure the time required for property accesses. Any 
>> thoughts on this?
>>
>> On Friday, 18 September 2015 16:30:42 UTC+5:30, Jakob Kummerow wrote:
>>>
>>> Property access time is not measured separately.
>>>
>>> On Fri, Sep 18, 2015 at 12:56 PM, dmonji  wrote:
>>>
 I want to compute the proportion of time spent on property accesses in 
 JavaScript programs. I am aware of 
 code.com/svn/branches/bleeding_edge/tools/profviz/profviz.html 
  which is a cpu profiler.

 But it is not clear what exactly does "execution" refer to since "ic 
 cache" is shown seperately?

 Does "execution" only include "Access time of properties"?

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Re: [v8-users] Property access time in JavaScript programs

2015-09-30 Thread Jakob Kummerow 
On Wed, Sep 30, 2015 at 2:55 PM, dmonji  wrote:

> What does the percentage mentioned in brackets refer to? Does ic miss
> (24.3%) means 24.3 % of total execution time was spent on inline cache
> misses?
>

Yes, including potential over-reporting.


> But surprisingly these percentages do not add to 100%.
>

Some ticks might not be attributable. Ticks outside V8 definitely don't
show up.


> Also, is it possible to see JITed code, where I can see how the code looks
> with inline caches?
>

--print-code for unoptimized code (right after being generated, i.e. all
ICs still uninitialized)
--print-opt-code for optimized code (same note)
--code-comments might help make sense of it all

--help for self-education


> I am aware of --trace_ic which gives out the information about
> LOADIC and STOREIC. But I want to see how the original code looks after
> introducing code for inline caching.
>

I don't know what you mean by "after introducing code for inline caching".
The call targets get patched, that's all... no code is added.


> On Friday, 18 September 2015 18:44:43 UTC+5:30, Jakob Kummerow wrote:
>>
>> I don't think it's possible to measure property access times directly.
>> One reason is that a single property access is much, much faster than
>> getting a timestamp from the operating system.
>>
>> So your best bet is probably to measure it indirectly: take a
>> long-running loop, add a single property access in such a way that (1) it
>> can't be optimized away by the compiler and (2) it doesn't introduce
>> additional operations, which isn't easy to achieve at the same time, and
>> measure how much longer the overall loop takes than it did before.
>>
>> Of course that would be a very artificial micro-benchmark, and would only
>> measure one very specific situation. In the general case, property accesses
>> can take *very* different amounts of time, though: in the best case,
>> they're a single machine instruction; in the worst case, they're thousands
>> of machine instructions. It all depends on so many things...
>>
>> I can't think of a way to take an existing program and accurately measure
>> what fraction of its running time is spent on property accesses.
>>
>> On Fri, Sep 18, 2015 at 1:13 PM, dmonji  wrote:
>>
>>> Is there any way to measure it?
>>>
>>> I tried to instrument the JavaScript code, and summed up the time
>>> between "before access" and "after access". But I am not very sure if this
>>> is
>>> the right way to measure the time required for property accesses. Any
>>> thoughts on this?
>>>
>>> On Friday, 18 September 2015 16:30:42 UTC+5:30, Jakob Kummerow wrote:

 Property access time is not measured separately.

 On Fri, Sep 18, 2015 at 12:56 PM, dmonji  wrote:

> I want to compute the proportion of time spent on property accesses in
> JavaScript programs. I am aware of
> code.com/svn/branches/bleeding_edge/tools/profviz/profviz.html
>  which is a cpu profiler.
>
> But it is not clear what exactly does "execution" refer to since "ic
> cache" is shown seperately?
>
> Does "execution" only include "Access time of properties"?
>
> --
>


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Re: [v8-users] Property access time in JavaScript programs

2015-09-18 Thread dmonji 
Is there any way to measure it? 

I tried to instrument the JavaScript code, and summed up the time between 
"before access" and "after access". But I am not very sure if this is
the right way to measure the time required for property accesses. Any 
thoughts on this?

On Friday, 18 September 2015 16:30:42 UTC+5:30, Jakob Kummerow wrote:
>
> Property access time is not measured separately.
>
> On Fri, Sep 18, 2015 at 12:56 PM, dmonji  > wrote:
>
>> I want to compute the proportion of time spent on property accesses in 
>> JavaScript programs. I am aware of 
>> code.com/svn/branches/bleeding_edge/tools/profviz/profviz.html 
>>  which is a cpu profiler.
>>
>> But it is not clear what exactly does "execution" refer to since "ic 
>> cache" is shown seperately?
>>
>> Does "execution" only include "Access time of properties"?
>>
>> -- 
>> -- 
>> v8-users mailing list
>> v8-u...@googlegroups.com 
>> http://groups.google.com/group/v8-users
>> --- 
>> You received this message because you are subscribed to the Google Groups 
>> "v8-users" group.
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>> email to v8-users+u...@googlegroups.com .
>> For more options, visit https://groups.google.com/d/optout.
>>
>
>

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Re: [v8-users] Property access time in JavaScript programs

2015-09-18 Thread Jakob Kummerow 
Property access time is not measured separately.

On Fri, Sep 18, 2015 at 12:56 PM, dmonji  wrote:

> I want to compute the proportion of time spent on property accesses in
> JavaScript programs. I am aware of
> code.com/svn/branches/bleeding_edge/tools/profviz/profviz.html
>  which is a cpu profiler.
>
> But it is not clear what exactly does "execution" refer to since "ic
> cache" is shown seperately?
>
> Does "execution" only include "Access time of properties"?
>
> --
> --
> v8-users mailing list
> v8-users@googlegroups.com
> http://groups.google.com/group/v8-users
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> You received this message because you are subscribed to the Google Groups
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Re: [v8-users] Property access time in JavaScript programs

2015-09-18 Thread Jakob Kummerow 
I don't think it's possible to measure property access times directly. One
reason is that a single property access is much, much faster than getting a
timestamp from the operating system.

So your best bet is probably to measure it indirectly: take a long-running
loop, add a single property access in such a way that (1) it can't be
optimized away by the compiler and (2) it doesn't introduce additional
operations, which isn't easy to achieve at the same time, and measure how
much longer the overall loop takes than it did before.

Of course that would be a very artificial micro-benchmark, and would only
measure one very specific situation. In the general case, property accesses
can take *very* different amounts of time, though: in the best case,
they're a single machine instruction; in the worst case, they're thousands
of machine instructions. It all depends on so many things...

I can't think of a way to take an existing program and accurately measure
what fraction of its running time is spent on property accesses.

On Fri, Sep 18, 2015 at 1:13 PM, dmonji  wrote:

> Is there any way to measure it?
>
> I tried to instrument the JavaScript code, and summed up the time between
> "before access" and "after access". But I am not very sure if this is
> the right way to measure the time required for property accesses. Any
> thoughts on this?
>
> On Friday, 18 September 2015 16:30:42 UTC+5:30, Jakob Kummerow wrote:
>>
>> Property access time is not measured separately.
>>
>> On Fri, Sep 18, 2015 at 12:56 PM, dmonji  wrote:
>>
>>> I want to compute the proportion of time spent on property accesses in
>>> JavaScript programs. I am aware of
>>> code.com/svn/branches/bleeding_edge/tools/profviz/profviz.html
>>>  which is a cpu profiler.
>>>
>>> But it is not clear what exactly does "execution" refer to since "ic
>>> cache" is shown seperately?
>>>
>>> Does "execution" only include "Access time of properties"?
>>>
>>> --
>>> --
>>> v8-users mailing list
>>> v8-u...@googlegroups.com
>>> http://groups.google.com/group/v8-users
>>> ---
>>> You received this message because you are subscribed to the Google
>>> Groups "v8-users" group.
>>> To unsubscribe from this group and stop receiving emails from it, send
>>> an email to v8-users+u...@googlegroups.com.
>>> For more options, visit https://groups.google.com/d/optout.
>>>
>>
>> --
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