Re: [go-nuts] How to obtain complete call chain of runtime functions in pprof, like 'mcall'

[Robert Engels]

I think they are relevant. It is because the profiler only records a record 
when there is a state transition, which is fine, but then the record needs to 
reflect it, and probably should at least point to the previous record - that is 
- use the same stack trace, so the accounting is correct. 

Seems like a bug to me but it doesn’t appear the Go team either felt the same, 
or had any desire to fix it. 

> On Mar 8, 2020, at 12:37 PM, Xiangdong JI  wrote:
> 
> 
> Thanks Robert, I'm trying to utilize the tool now, the new output rendered by 
> goanalyzer contains a page for PC:0 goroutines, which were discussed in 
> #29103, but seems no further details are available, are they considered 
> irrelevant to perf. analysis? 
> 
>> On Thursday, March 5, 2020 at 8:09:18 PM UTC+8, Robert Engels wrote:
>> You might be interested in github.com/robaho/go-analyzer which I believe 
>> significantly improves the profiling information when dealing with highly 
>> concurrent Go programs. 
>> 
 On Mar 5, 2020, at 12:13 AM, Xiangdong JI  wrote:
 
>>> 
>>> Thanks Ian.
>>> 
>>> I'm using schedtrace and scheddetail to help understand the scheduling 
>>> flow, the minimum monitoring window seems to be 1ms only, possible to get 
>>> more detailed info?
>>> Furthermore, sched* outputs extensive logs but what I expect, at present, 
>>> might be something like when a goroutine is parked due to what reason, 
>>> etc., can I get it with the existing diagnostics?  
>>>  
>>> 
 On Thursday, March 5, 2020 at 11:24:23 AM UTC+8, Ian Lance Taylor wrote:
 On Wed, Mar 4, 2020 at 6:44 PM Xiangdong JI  wrote: 
 > 
 > Given the attached screenshot of pprof output, I wonder how to figure 
 > out the callers of 'runtime.mcall' and their cost? Thanks. 
 
 You can't, but it doesn't matter.  The mcall function is used when a 
 thread changes from executing one goroutine to a different goroutine. 
 Knowing the code that triggers the call into mcall won't tell you 
 anything.  It's just where that goroutine happened to be preempted. 
 
 Ian 
>>> 
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> 
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Re: [go-nuts] How to obtain complete call chain of runtime functions in pprof, like 'mcall'

[Xiangdong JI]

Thanks Robert, I'm trying to utilize the tool now, the new output rendered 
by goanalyzer contains a page for PC:0 goroutines, which were discussed in 
#29103 , but seems no further 
details are available, are they considered irrelevant to perf. analysis? 

On Thursday, March 5, 2020 at 8:09:18 PM UTC+8, Robert Engels wrote:
>
> You might be interested in github.com/robaho/go-analyzer which I believe 
> significantly improves the profiling information when dealing with highly 
> concurrent Go programs. 
>
> On Mar 5, 2020, at 12:13 AM, Xiangdong JI > 
> wrote:
>
> 
> Thanks Ian.
>
> I'm using schedtrace and scheddetail to help understand the scheduling 
> flow, the minimum monitoring window seems to be 1ms only, possible to get 
> more detailed info?
> Furthermore, sched* outputs extensive logs but what I expect, at present, 
> might be something like when a goroutine is parked due to what reason, 
> etc., can I get it with the existing diagnostics?  
>  
>
> On Thursday, March 5, 2020 at 11:24:23 AM UTC+8, Ian Lance Taylor wrote:
>>
>> On Wed, Mar 4, 2020 at 6:44 PM Xiangdong JI  wrote: 
>> > 
>> > Given the attached screenshot of pprof output, I wonder how to figure 
>> out the callers of 'runtime.mcall' and their cost? Thanks. 
>>
>> You can't, but it doesn't matter.  The mcall function is used when a 
>> thread changes from executing one goroutine to a different goroutine. 
>> Knowing the code that triggers the call into mcall won't tell you 
>> anything.  It's just where that goroutine happened to be preempted. 
>>
>> Ian 
>>
> -- 
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>  
> 
> .
>
>

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Re: [go-nuts] How to obtain complete call chain of runtime functions in pprof, like 'mcall'

[Ian Lance Taylor]

On Wed, Mar 4, 2020 at 10:12 PM Xiangdong JI  wrote:
>
> I'm using schedtrace and scheddetail to help understand the scheduling flow, 
> the minimum monitoring window seems to be 1ms only, possible to get more 
> detailed info?
> Furthermore, sched* outputs extensive logs but what I expect, at present, 
> might be something like when a goroutine is parked due to what reason, etc., 
> can I get it with the existing diagnostics?

Calling runtime.Stack(buf, true) should tell you for each parked
goroutine why it is parked.  Of course it will also give you a lot
more that you don't care about, like the stack backtraces.

Ian


>
> On Thursday, March 5, 2020 at 11:24:23 AM UTC+8, Ian Lance Taylor wrote:
>>
>> On Wed, Mar 4, 2020 at 6:44 PM Xiangdong JI  wrote:
>> >
>> > Given the attached screenshot of pprof output, I wonder how to figure out 
>> > the callers of 'runtime.mcall' and their cost? Thanks.
>>
>> You can't, but it doesn't matter.  The mcall function is used when a
>> thread changes from executing one goroutine to a different goroutine.
>> Knowing the code that triggers the call into mcall won't tell you
>> anything.  It's just where that goroutine happened to be preempted.
>>
>> Ian
>
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Re: [go-nuts] How to obtain complete call chain of runtime functions in pprof, like 'mcall'

[Jake Montgomery]

I think you meant https://github.com/robaho/goanalyzer

On Thursday, March 5, 2020 at 7:09:18 AM UTC-5, Robert Engels wrote:
>
> You might be interested in github.com/robaho/go-analyzer which I believe 
> significantly improves the profiling information when dealing with highly 
> concurrent Go programs. 
>
> On Mar 5, 2020, at 12:13 AM, Xiangdong JI > 
> wrote:
>
> 
> Thanks Ian.
>
> I'm using schedtrace and scheddetail to help understand the scheduling 
> flow, the minimum monitoring window seems to be 1ms only, possible to get 
> more detailed info?
> Furthermore, sched* outputs extensive logs but what I expect, at present, 
> might be something like when a goroutine is parked due to what reason, 
> etc., can I get it with the existing diagnostics?  
>  
>
> On Thursday, March 5, 2020 at 11:24:23 AM UTC+8, Ian Lance Taylor wrote:
>>
>> On Wed, Mar 4, 2020 at 6:44 PM Xiangdong JI  wrote: 
>> > 
>> > Given the attached screenshot of pprof output, I wonder how to figure 
>> out the callers of 'runtime.mcall' and their cost? Thanks. 
>>
>> You can't, but it doesn't matter.  The mcall function is used when a 
>> thread changes from executing one goroutine to a different goroutine. 
>> Knowing the code that triggers the call into mcall won't tell you 
>> anything.  It's just where that goroutine happened to be preempted. 
>>
>> Ian 
>>
> -- 
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> "golang-nuts" group.
> To unsubscribe from this group and stop receiving emails from it, send an 
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> To view this discussion on the web visit 
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>  
> 
> .
>
>

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Re: [go-nuts] How to obtain complete call chain of runtime functions in pprof, like 'mcall'

[Robert Engels]

You might be interested in github.com/robaho/go-analyzer which I believe 
significantly improves the profiling information when dealing with highly 
concurrent Go programs. 

> On Mar 5, 2020, at 12:13 AM, Xiangdong JI  wrote:
> 
> 
> Thanks Ian.
> 
> I'm using schedtrace and scheddetail to help understand the scheduling flow, 
> the minimum monitoring window seems to be 1ms only, possible to get more 
> detailed info?
> Furthermore, sched* outputs extensive logs but what I expect, at present, 
> might be something like when a goroutine is parked due to what reason, etc., 
> can I get it with the existing diagnostics?  
>  
> 
>> On Thursday, March 5, 2020 at 11:24:23 AM UTC+8, Ian Lance Taylor wrote:
>> On Wed, Mar 4, 2020 at 6:44 PM Xiangdong JI  wrote: 
>> > 
>> > Given the attached screenshot of pprof output, I wonder how to figure out 
>> > the callers of 'runtime.mcall' and their cost? Thanks. 
>> 
>> You can't, but it doesn't matter.  The mcall function is used when a 
>> thread changes from executing one goroutine to a different goroutine. 
>> Knowing the code that triggers the call into mcall won't tell you 
>> anything.  It's just where that goroutine happened to be preempted. 
>> 
>> Ian 
> 
> -- 
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Re: [go-nuts] How to obtain complete call chain of runtime functions in pprof, like 'mcall'

[Xiangdong JI]

Thanks Ian.

I'm using schedtrace and scheddetail to help understand the scheduling 
flow, the minimum monitoring window seems to be 1ms only, possible to get 
more detailed info?
Furthermore, sched* outputs extensive logs but what I expect, at present, 
might be something like when a goroutine is parked due to what reason, 
etc., can I get it with the existing diagnostics?  
 

On Thursday, March 5, 2020 at 11:24:23 AM UTC+8, Ian Lance Taylor wrote:
>
> On Wed, Mar 4, 2020 at 6:44 PM Xiangdong JI  > wrote: 
> > 
> > Given the attached screenshot of pprof output, I wonder how to figure 
> out the callers of 'runtime.mcall' and their cost? Thanks. 
>
> You can't, but it doesn't matter.  The mcall function is used when a 
> thread changes from executing one goroutine to a different goroutine. 
> Knowing the code that triggers the call into mcall won't tell you 
> anything.  It's just where that goroutine happened to be preempted. 
>
> Ian 
>

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Re: [go-nuts] How to obtain complete call chain of runtime functions in pprof, like 'mcall'

[Ian Lance Taylor]

On Wed, Mar 4, 2020 at 6:44 PM Xiangdong JI  wrote:
>
> Given the attached screenshot of pprof output, I wonder how to figure out the 
> callers of 'runtime.mcall' and their cost? Thanks.

You can't, but it doesn't matter.  The mcall function is used when a
thread changes from executing one goroutine to a different goroutine.
Knowing the code that triggers the call into mcall won't tell you
anything.  It's just where that goroutine happened to be preempted.

Ian

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[go-nuts] How to obtain complete call chain of runtime functions in pprof, like 'mcall'

[Xiangdong JI]

Hi,

Given the attached screenshot of pprof output, I wonder how to figure out 
the callers of 'runtime.mcall' and their cost? Thanks.

(The image is generated by profiling BenchmarkGoroutineBlocking).

[image: Capture.JPG]


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