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[Bugfix][Kernel] Implement acquire/release polyfill for Pascal #8776

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merged 4 commits into from
Sep 25, 2024
Merged

[Bugfix][Kernel] Implement acquire/release polyfill for Pascal #8776

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439e60d
[Bugfix] Implement acquire/release polyfill for Pascal
sasha0552 Sep 24, 2024
68307b3
drop .sys modifier from ld
sasha0552 Sep 24, 2024
3c4d070
fix test
sasha0552 Sep 24, 2024
eb4bea2
fix "sleep" time
sasha0552 Sep 24, 2024
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11 changes: 11 additions & 0 deletions csrc/custom_all_reduce.cuh
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Original file line number Diff line number Diff line change
Expand Up @@ -131,15 +131,26 @@ DINLINE O downcast(array_t<float, O::size> val) {
}

static DINLINE void st_flag_release(FlagType* flag_addr, FlagType flag) {
#if defined(__CUDA_ARCH__) && __CUDA_ARCH__ >= 700
asm volatile("st.release.sys.global.u32 [%1], %0;" ::"r"(flag),
"l"(flag_addr));
#else
asm volatile("membar.sys; st.volatile.global.u32 [%1], %0;" ::"r"(flag),
"l"(flag_addr));
#endif
}

static DINLINE FlagType ld_flag_acquire(FlagType* flag_addr) {
FlagType flag;
#if defined(__CUDA_ARCH__) && __CUDA_ARCH__ >= 700
asm volatile("ld.acquire.sys.global.u32 %0, [%1];"
: "=r"(flag)
: "l"(flag_addr));
#else
asm volatile("ld.volatile.global.u32 %0, [%1]; membar.gl;"
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In the NCCL polyfill there's a .sys scope here. Should we also include it here?

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@sasha0552 sasha0552 Sep 25, 2024 •
edited
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I tried that first, but got an error: Modifier '.volatile' cannot be combined with modifier '.sys' (build log). I wonder why this works for NCCL, but as I read in the documentation, .volatile implies .sys (?).

ld.volatile has the same memory synchronization semantics as ld.relaxed.sys.

-- https://docs.nvidia.com/cuda/parallel-thread-execution/index.html

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That makes sense. Thanks.

: "=r"(flag)
: "l"(flag_addr));
#endif
return flag;
}

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7 changes: 7 additions & 0 deletions csrc/custom_all_reduce_test.cu
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Expand Up @@ -44,7 +44,14 @@
} while (0)

__global__ void dummy_kernel() {
#if defined(__CUDA_ARCH__) && __CUDA_ARCH__ >= 700
for (int i = 0; i < 100; i++) __nanosleep(1000000); // 100ms
#else
for (int i = 0; i < 100; i++) {
long long int start = clock64();
while (clock64() - start < 150000000); // approximately 98.4ms on P40
}
#endif
}

template <typename T>
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