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Magic-trace – High-resolution traces of what a process is doing

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Re: Magic-trace – High-resolution traces of what a process is doing

#21

Post by DonaldPShimoda »

nojito wrote: post #20
DonaldPShimoda wrote: post #17

Earlier quoted context omitted.

They are among the most notable users of OCaml in the world, and have taken significant stewardship of the language. They sponsor, attend, and publish at multiple academic conferences, especially in the realm of programming languages. I don't think I can say I support their company's primary mission, but their commitment to improving the world of software through various means (language influence, academic publicatio…

Partly because the cost of switching is impossible for them.

You think they are platinum-level sponsors at multiple conferences every year, sponsors of PLMW multiple times a year, sponsors for carbon-neutrality at ICFP each year, and continue investing in hiring PhDs and improving the OCaml ecosystem because... the... cost of switching away from OCaml is too great?

I don't think that tracks. They like OCaml, and they are pretty adamant that it is a good tool for the job. Maybe you disagree, but you should not project your opinions on them.

Re: Magic-trace – High-resolution traces of what a process is doing

#22

Post by t_mann »

DonaldPShimoda wrote: post #17
t_mann wrote: post #8

Jane Street is a prop trading shop. I heard that they take tech seriously, but still impressed to see them at the front of HN with a tool like this.

They are among the most notable users of OCaml in the world, and have taken significant stewardship of the language. They sponsor, attend, and publish at multiple academic conferences, especially in the realm of programming languages. I don't think I can say I support their company's primary mission, but their commitment to improving the world of software through various means (language influence, academic publicatio…

Yeah, quite impressive language to make the backbone of all your systems.

Re: Magic-trace – High-resolution traces of what a process is doing

#24

Post by geuis »

cgaebel wrote: post #2

Hi HN! I'm Clark, one of the maintainers of magic-trace. magic-trace was submitted before, our first announcement was this blog post: https://blog.janestreet.com/magic-trace/ . Since then, we've worked hard at making magic-trace more accessible to outside users. We've heard stories of people thinking this was cool before but being unable to even find a download link. I'm posting this here because we just released "ve…

On the website, scrolling doesn't work in mobile safari.

Re: Magic-trace – High-resolution traces of what a process is doing

#26

Post by rrss »

Scaevolus wrote: post #23

If you just want calls and returns, can't you use one of the other PMUs for that? Or is sampling at the "1 sample per event" level higher overhead than IPT?

do you mean configuring the other PMUs to interrupt the core every function call / return?

If yes, then yes that is much much higher overhead than processor trace.

Re: Magic-trace – High-resolution traces of what a process is doing

#27

Post by skrebbel »

DonaldPShimoda wrote: post #21
nojito wrote: post #20

Earlier quoted context omitted.

Partly because the cost of switching is impossible for them.

You think they are platinum-level sponsors at multiple conferences every year, sponsors of PLMW multiple times a year, sponsors for carbon-neutrality at ICFP each year, and continue investing in hiring PhDs and improving the OCaml ecosystem because... the... cost of switching away from OCaml is too great? I don't think that tracks. They like OCaml, and they are pretty adamant that it is a good tool for the job. Maybe…

I bet it is also a great way for them to hire and retain great engineers, including the kind that isn't just in it for the money.

Re: Magic-trace – High-resolution traces of what a process is doing

#28

Post by nemetroid »

> The key difference from perf is that instead of sampling call stacks throughout time, magic-trace uses Intel Processor Trace to snapshot a ring buffer of all control flow leading up to a chosen point in time[2].

> 2. perf can do this too, but that's not how most people use it. In fact, if you peek under the hood you'll see that magic-trace uses perf to drive Intel PT.

I think this (the first sentence quoted) is a bit misleading. The main feature is not really a "key difference from perf" if the main feature is implemented using perf. From a brief read, it looks like the real key difference is a friendlier and more interactive UI (both when capturing and viewing the trace).

Regardless, I think it looks neat, and will try to take it for a spin sometime soon.

Re: Magic-trace – High-resolution traces of what a process is doing

#29

Post by jeffbee »

electroly wrote: post #10

Looks really cool. I'm sad that I'll never know; Intel + Linux + non-VM excludes literally every computer I have access to. We're all AMD + Windows, and my only access to Intel Linux machines would be a cloud VM.

You can use PMUs in the cloud. Amazon's c6i.metal instance type is an Intel Ice Lake Xeon with full PMU access, for example.

Re: Magic-trace – High-resolution traces of what a process is doing

#30

Post by DonaldPShimoda »

skrebbel wrote: post #27
DonaldPShimoda wrote: post #21

Earlier quoted context omitted.

You think they are platinum-level sponsors at multiple conferences every year, sponsors of PLMW multiple times a year, sponsors for carbon-neutrality at ICFP each year, and continue investing in hiring PhDs and improving the OCaml ecosystem because... the... cost of switching away from OCaml is too great? I don't think that tracks. They like OCaml, and they are pretty adamant that it is a good tool for the job. Maybe…

I bet it is also a great way for them to hire and retain great engineers, including the kind that isn't just in it for the money.

Speaking only of what I see (I'm a PhD student in the field of programming languages), quite a few people seek internships and full-time employment with JS specifically because of the tech stack and the kind of problems they (JS) tend to like throwing themselves at. They do some seriously cool stuff, and they've published a lot of great research!
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