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Posted to reviews@mesos.apache.org by Ilya Pronin <ip...@twopensource.com> on 2017/07/04 10:55:26 UTC
Re: Review Request 60003: Reduced copying in defer,
dispatch and Future.
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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/60003/#review179373
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3rdparty/libprocess/include/process/deferred.hpp
Line 77 (original), 79 (patched)
<https://reviews.apache.org/r/60003/#comment254039>
This is more a question than an issue. Do we plan to forward functor references through `_Deferred`, hence the use of `std::forward<F>()` here instead of `std::move()`?
Carrying a functor reference is unsafe. `template <typename F> _Deferred<F> defer(F&&)` overload silently captures references to lvalues in `_Deferred<F&>`. But as long as `_Deferred` is immediately used for conversion to `Deferred` or `std::function` it should be fine.
3rdparty/libprocess/include/process/deferred.hpp
Lines 83-88 (original), 85-90 (patched)
<https://reviews.apache.org/r/60003/#comment254283>
Can we eliminate more copyings here? `f_` is captured by value by lambda and then passed as a `const` to `dispatch`. We can make the lambda `mutable` and `move()` captured `f_`. Or, for example, we could store `f` value and `pid` in a structure, that will be captured by a `std::shared_ptr`.
3rdparty/libprocess/include/process/dispatch.hpp
Lines 203-205 (patched)
<https://reviews.apache.org/r/60003/#comment254244>
Style: `Dispatcher` internals are overindented. Here and in other places where it's defined.
- Ilya Pronin
On June 15, 2017, 8:32 a.m., Dmitry Zhuk wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/60003/
> -----------------------------------------------------------
>
> (Updated June 15, 2017, 8:32 a.m.)
>
>
> Review request for mesos, Benjamin Hindman, haosdent huang, James Peach, and Michael Park.
>
>
> Bugs: MESOS-7713
> https://issues.apache.org/jira/browse/MESOS-7713
>
>
> Repository: mesos
>
>
> Description
> -------
>
> Reduced copying in defer, dispatch and Future.
>
> This reduces number of copies made for each parameter in a code like this:
> future.then(defer(pid, &SomeProcess::someMethod, param1, param2));
>
> For the objects that do not support move semantics (e.g. protobuf messages), number of copies is reduced from 8-10 to 6. If move semantics is supported, then number of copies is reduced from 6-7 to 1 if parameter is passed with std::move, or 2 otherwise.
>
>
> Diffs
> -----
>
> 3rdparty/libprocess/include/process/defer.hpp 7f3369e723cb244e97930621cbba89cf7873567d
> 3rdparty/libprocess/include/process/deferred.hpp e446621be11ac51f5f91c417cc8975e363c2f715
> 3rdparty/libprocess/include/process/dispatch.hpp 3a0793888dc0df5e3ec31b06f47cd920c71e0db9
> 3rdparty/libprocess/include/process/future.hpp cce950509f58022e79bb51a6e72ea1a005b9cb50
> 3rdparty/libprocess/include/process/http.hpp f637999174d92a98208b5fc49a65f9929efb11a0
>
>
> Diff: https://reviews.apache.org/r/60003/diff/1/
>
>
> Testing
> -------
>
> make check
>
> Number of copies was checked by using defer to subscribe process for Future callbacks, and passing parameters that count number of copies made.
>
>
> Thanks,
>
> Dmitry Zhuk
>
>
Re: Review Request 60003: Reduced copying in defer,
dispatch and Future.
Posted by Dmitry Zhuk <dz...@twopensource.com>.
> On July 4, 2017, 10:55 a.m., Ilya Pronin wrote:
> > 3rdparty/libprocess/include/process/deferred.hpp
> > Line 77 (original), 79 (patched)
> > <https://reviews.apache.org/r/60003/diff/1/?file=1748112#file1748112line79>
> >
> > This is more a question than an issue. Do we plan to forward functor references through `_Deferred`, hence the use of `std::forward<F>()` here instead of `std::move()`?
> >
> > Carrying a functor reference is unsafe. `template <typename F> _Deferred<F> defer(F&&)` overload silently captures references to lvalues in `_Deferred<F&>`. But as long as `_Deferred` is immediately used for conversion to `Deferred` or `std::function` it should be fine.
This is intentional, as in this case move/copy happens only once on conversion. Saving `f` by value would add an extra move/copy on `_Deferred` construction.
This implementation is relatively safe, as `_Deferred` is documented as an intermediate type, which is not supposed to be used directly, and it's somewhat protected from misuse by having public methods callable on rvalues only.
> On July 4, 2017, 10:55 a.m., Ilya Pronin wrote:
> > 3rdparty/libprocess/include/process/deferred.hpp
> > Lines 83-88 (original), 85-90 (patched)
> > <https://reviews.apache.org/r/60003/diff/1/?file=1748112#file1748112line85>
> >
> > Can we eliminate more copyings here? `f_` is captured by value by lambda and then passed as a `const` to `dispatch`. We can make the lambda `mutable` and `move()` captured `f_`. Or, for example, we could store `f` value and `pid` in a structure, that will be captured by a `std::shared_ptr`.
We can't assume that lambda is called only once here, so we must make a copy. Avoiding this last copy is doable, but I left it out of scope of this review.
- Dmitry
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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/60003/#review179373
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On July 17, 2017, 11:42 a.m., Dmitry Zhuk wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/60003/
> -----------------------------------------------------------
>
> (Updated July 17, 2017, 11:42 a.m.)
>
>
> Review request for mesos, Benjamin Hindman, haosdent huang, James Peach, and Michael Park.
>
>
> Bugs: MESOS-7713
> https://issues.apache.org/jira/browse/MESOS-7713
>
>
> Repository: mesos
>
>
> Description
> -------
>
> This reduces number of copies made for each parameter in a code like this:
> future.then(defer(pid, &SomeProcess::someMethod, param1, param2));
>
> For the objects that do not support move semantics (e.g. protobuf messages), number of copies is reduced from 8-10 to 6. If move semantics is supported, then number of copies is reduced from 6-7 to 1 if parameter is passed with std::move, or 2 otherwise.
>
>
> Diffs
> -----
>
> 3rdparty/libprocess/include/process/defer.hpp 7f3369e723cb244e97930621cbba89cf7873567d
> 3rdparty/libprocess/include/process/deferred.hpp e446621be11ac51f5f91c417cc8975e363c2f715
> 3rdparty/libprocess/include/process/dispatch.hpp 3a0793888dc0df5e3ec31b06f47cd920c71e0db9
> 3rdparty/libprocess/include/process/future.hpp cce950509f58022e79bb51a6e72ea1a005b9cb50
> 3rdparty/libprocess/include/process/http.hpp f637999174d92a98208b5fc49a65f9929efb11a0
>
>
> Diff: https://reviews.apache.org/r/60003/diff/2/
>
>
> Testing
> -------
>
> make check
>
> Number of copies was checked by using defer to subscribe process for Future callbacks, and passing parameters that count number of copies made.
>
>
> Thanks,
>
> Dmitry Zhuk
>
>