I'm trying to tweak the GC when compiling with dub, starting with something easy like profile:1.

> $ grep dflags dub.json
>     "dflags": [ "-lowmem", "--DRT-gcopt=profile:1" ],
> $ dub test

Doesn't work, doesn't give any extra output. Entering bogus flags like --DRT-gcopt=banana:1 doesn't evoke any error message either, making me doubt it's being passed on at all.

> $ dmd -oftest -lowmem --DRT-gcopt=profile:1 source/**/*.d
>         Number of collections:  13
>         Total GC prep time:  7 milliseconds
>         Total mark time:  2110 milliseconds
>         Total sweep time:  270 milliseconds
>         Total page recovery time:  204 milliseconds
>         Max Pause Time:  472 milliseconds
>         Grand total GC time:  2592 milliseconds
> GC summary: 1099 MB,   13 GC 2592 ms, Pauses 2117 ms <  472 ms

Manual dmd invocation does work, so it's not like dmd is ignoring --DRT-gcopt.

> $ dub test --DRT-gcopt=profile:1
> [...]
>         Number of collections:  10
>         Total GC prep time:  0 milliseconds
>         Total mark time:  4 milliseconds
>         Total sweep time:  7 milliseconds
>         Total page recovery time:  4 milliseconds
>         Max Pause Time:  0 milliseconds
>         Grand total GC time:  15 milliseconds
> GC summary:   12 MB,   10 GC   15 ms, Pauses    4 ms <    0 ms

The totals should be in the ballpark of 1Gb+ (as above), not 12Mb. Is it only profiling dub itself? (Incidentally this is roughly what dmd reports if called without -lowmem.)

> $ export DRT_GCOPT=profile:1
> $ dub test

Doesn't work either, I can't actually get the env var to affect dmd at all, even when manually running it.

What is the correct way?

On Friday, 31 May 2019 at 10:27:44 UTC, Anonymouse wrote:

> What is the correct way?

--DRT flags are for run time, not compile time. They're intended to be passed to your executable and not the compiler. From the docs [1]:

"By default, GC options can only be passed on the command line of the program to run"

With dub, anything following a solitary -- on the command line will be passed to the application [2], so you probably want something like this:

dub test -- --DRT-gcopt=profile:1

[1] https://dlang.org/spec/garbage.html#gc_config
[2] https://dub.pm/commandline

On Friday, 31 May 2019 at 10:47:20 UTC, Mike Parker wrote:
> On Friday, 31 May 2019 at 10:27:44 UTC, Anonymouse wrote:
>
>> What is the correct way?
>
> --DRT flags are for run time, not compile time. They're intended to be passed to your executable and not the compiler. From the docs [1]:
>
> "By default, GC options can only be passed on the command line of the program to run"

My use-case is limiting the amount of memory dmd will allocate before -lowmem kicks in and collects (by use of --DRT-gcopt=heapSizeFactor on dmd), to accomodate for limited available memory. As pasted in the original post I seem to be able to do this manually.

So there is no way to set up a dub build configuration that automates this?

On Friday, 31 May 2019 at 10:47:20 UTC, Mike Parker wrote:
> On Friday, 31 May 2019 at 10:27:44 UTC, Anonymouse wrote:
>
>> What is the correct way?
>
> --DRT flags are for run time, not compile time. They're intended to be passed to your executable and not the compiler. From the docs [1]:
>
> "By default, GC options can only be passed on the command line of the program to run"
>
> With dub, anything following a solitary -- on the command line will be passed to the application [2], so you probably want something like this:
>
> dub test -- --DRT-gcopt=profile:1
>
> [1] https://dlang.org/spec/garbage.html#gc_config
> [2] https://dub.pm/commandline

This might be eaten by the runtime of dub and not the application.

Kind regards
Andre

On Friday, 31 May 2019 at 13:37:05 UTC, Anonymouse wrote:
> On Friday, 31 May 2019 at 10:47:20 UTC, Mike Parker wrote:
>> On Friday, 31 May 2019 at 10:27:44 UTC, Anonymouse wrote:
>>
>>> What is the correct way?
>>
>> --DRT flags are for run time, not compile time. They're intended to be passed to your executable and not the compiler. From the docs [1]:
>>
>> "By default, GC options can only be passed on the command line of the program to run"
>
> My use-case is limiting the amount of memory dmd will allocate before -lowmem kicks in and collects (by use of --DRT-gcopt=heapSizeFactor on dmd), to accomodate for limited available memory. As pasted in the original post I seem to be able to do this manually.
>
> So there is no way to set up a dub build configuration that automates this?

You can specify the parameters also in code. See example here

https://dlang.org/changelog/2.085.0.html#gc_cleanup

Kind regards
Andre

On Friday, 31 May 2019 at 10:27:44 UTC, Anonymouse wrote:
>> $ grep dflags dub.json
>>     "dflags": [ "-lowmem", "--DRT-gcopt=profile:1" ],

This should work indeed. I guess it doesn't because dub probably uses a response file containing all cmdline options, whereas -lowmem definitely [and --DRT-* probably] need to be direct cmdline args.

On Friday, 31 May 2019 at 13:50:57 UTC, Andre Pany wrote:
> You can specify the parameters also in code. See example here
>
> https://dlang.org/changelog/2.085.0.html#gc_cleanup

I need it to apply to dmd though, I'm exceeding memory limits when compiling. Once done the program doesn't need a whole lot of it, but dmd -lowmem does.

On Friday, 31 May 2019 at 15:31:13 UTC, kinke wrote:
> On Friday, 31 May 2019 at 10:27:44 UTC, Anonymouse wrote:
>>> $ grep dflags dub.json
>>>     "dflags": [ "-lowmem", "--DRT-gcopt=profile:1" ],
>
> This should work indeed. I guess it doesn't because dub probably uses a response file containing all cmdline options, whereas -lowmem definitely [and --DRT-* probably] need to be direct cmdline args.

Is this something I can/should report? (Where do dub issues go?)

On Friday, 31 May 2019 at 15:41:24 UTC, Anonymouse wrote:
> On Friday, 31 May 2019 at 15:31:13 UTC, kinke wrote:
>> On Friday, 31 May 2019 at 10:27:44 UTC, Anonymouse wrote:
>>>> $ grep dflags dub.json
>>>>     "dflags": [ "-lowmem", "--DRT-gcopt=profile:1" ],
>>
>> This should work indeed. I guess it doesn't because dub probably uses a response file containing all cmdline options, whereas -lowmem definitely [and --DRT-* probably] need to be direct cmdline args.
>
> Is this something I can/should report? (Where do dub issues go?)

Replying here despite the delay because this is one of the top post when one google for gcopts.

This will be possible with the new version of the runtime (>=2.091.0, not released yet).

It has been filled as https://issues.dlang.org/show_bug.cgi?id=20459 and was fixed in https://github.com/dlang/druntime/pull/2881 which means dub compiled with druntime >= 2.091 will allow you to do:
`dub -- --DRT-gcopt=profile:1`

And any other D program will ignore `--DRT` options if provided after the `--` delimiter.