Thanks Alon! So here is something very weird. I could get the memory usage
go all the way to 2GB when I changed my testing code. This was my original
test code. So basically I was just adding elements to std::vector
infinitely.
class TestClass{
private:
int t = 0;
};
struct Data {
int t;
TestClass obj;
};
typedef std::vector<Data> Vec;
Vec someVec;
using namespace std;
int main() {
printf("hello, world!\n");
while(1){
Data data;
someVec.push_back(data);
}
return 0;
}
With this code, the WASM memory was going all the way to 1GB.
But when I changed the code to this, where I am writing some value after
acquiring memory, then I am able to see the memory usage go all the way up
to 2 GB. Could this be a bug? I am on emscripten 2.0.
int main() {
printf("hello, world!\n");
char *p = nullptr;
int byteSize = 50 * 1024 * 1024;
while(1){
p = new char(byteSize);
p[byteSize] = 20;
}
return 0;
}
Also It is very encouraging to see that 4GB is considered for PThreads as
well! Thanks.
One follow up question. May be a dumb one. What could be the potential
problems with ALLOW_MEMORY_GROWTH missing in PThreads mode? I see that when
the Wasm is instantiated, the overall memory that the Chrome tab was taking
was similar to the one taken by the WASM built with ALLOW_MEMORY_GROWTH. Is
it that, we will not be able to instantiate WASM on low end devices if
built with ALLOW_MEMORY_GROWTH=0?
Greatly appreciate your help Alon!
Thanks,
Prashanth Nethi
On Saturday, August 22, 2020 at 1:50:57 AM UTC+5:30 [email protected] wrote:
> I think you can do any number up to 2GB, including 2GB - 64Kb. So the
> limit isn't 1GB, unless you see that on some specific browser? Could be a
> bug.
>
> It should soon be possible to do up to 4GB for the initial memory (without
> growth), thanks to a spec change,
> https://github.com/WebAssembly/spec/pull/1174
>
> On Thu, Aug 20, 2020 at 8:10 AM Prashanth Nethi <[email protected]>
> wrote:
>
>> Hi,
>>
>> I am currently building WASM with the following flags, to enable PThreads
>> in Wasm.
>> -s USING_PTHREADS=1 -s INITIAL_MEMORY=1999MB -s MAXIMUM_MEMORY=2GB.
>>
>> This works wonderfully for our use cases! In fact we are able to get 2x
>> performance in some cases!
>>
>> When I checked the max memory that the Wasm could use, with PThreads
>> enabled, it got capped at 1 GB. I am seeing that when the WASM is built
>> with ALLOW_MEMORY_GROWTH, the Wasm can use upto 2GB. I know that
>> ALLOW_MEMORY_GROWTH with USE_PTHREADS is discouraged so can't look at that
>> as a possible solution.
>>
>> Is there anyway I can get Wasm to use 2GB (or even potentially 4GB in the
>> future) with PThreads enabled? Is it that I am missing using some
>> configuration options?
>>
>> I am really hoping there is a way to increase the WASM cap to 2GB, as
>> using PThreads, solves our use cases in a big way.
>>
>> Thanks,
>> Prashanth Nethi
>>
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