Re: [Caml-list] Profiling ocaml with lwt

[Kasper Janssens <Kasper.Janssens@hgst.com>]

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Yes, considered that, but the thing is, there are quite q few functions that would need to be wrapped, on two slightly different code bases. It doesn’t seem very feasible but it might be what I’ll have to resort to.
Other than that, isn’t that an error prone approach when lwt swaps to another thread in the mean time? Don’t you run the risk of timing not just your call but also everything that is done in between (e.g. Having lwt swapping in another thread in the mean time, won’t that show in the timing as well?)?

Kasper

From: Malcolm Matalka <mmatalka@gmail.com<mailto:mmatalka@gmail.com>>
Date: Wednesday 9 March 2016 at 10:49
To: Kasper <Kasper.Janssens@hgst.com<mailto:Kasper.Janssens@hgst.com>>
Cc: caml-list <caml-list@inria.fr<mailto:caml-list@inria.fr>>
Subject: Re: [Caml-list] Profiling ocaml with lwt


Generally I wrap external calls in something that gets that gets the wall time of an external service call and logs it somewhere.

Den 9 mar 2016 9:54 fm skrev "Kasper Janssens" <Kasper.Janssens@hgst.com<mailto:Kasper.Janssens@hgst.com>>:

Hello,


I’m trying to profile an ocaml application that has a performance degradation of about 20 %, with quite some code changes between both versions. I tried attaching perf and gprof to it, but to no real avail. Sure, there are slight differences in the running time of functions in the gprof result, but nothing whatsoever that seems to explain that kind of delay. Perf doesn’t seem to indicate a problem neither.


The thing is, I think it’s a delay in one of the servers that the application communicates with. The communication to those servers is done asynchronously, through lwt (epoll). I suspect that is the reason why delays in that communication don’t show up in the gprof result, but I’m not really sure.


Does anybody know of a way to profile lwt applications in a way that these kinds of delays might show up so I know which backend system I have to focus on?


Kasper

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