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Merge pull request #5133 from danlark1/reliable_lfalloc

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LfAlloc more reliable choice of hint
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Danila Kutenin 2019-04-28 14:45:59 +03:00 committed by GitHub
commit a76e504f45
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1 changed files with 9 additions and 2 deletions
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11
contrib/lfalloc/src/lf_allocX64.h
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@ -358,8 +358,15 @@ static char* AllocWithMMap(uintptr_t sz, EMMapMode mode) {
}
#if defined(USE_LFALLOC_RANDOM_HINT)
static thread_local std::mt19937_64 generator(std::random_device{}());
std::uniform_int_distribution<intptr_t> distr(areaStart, areaFinish / 2);
char* largeBlock = (char*)mmap(reinterpret_cast<void*>(distr(generator)), sz, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
std::uniform_int_distribution<intptr_t> distr(areaStart, areaFinish - sz - 1);
char* largeBlock;
static constexpr size_t MaxAttempts = 100;
size_t attempt = 0;
do
{
largeBlock = (char*)mmap(reinterpret_cast<void*>(distr(generator)), sz, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
++attempt;
} while (uintptr_t(((char*)largeBlock - ALLOC_START) + sz) >= areaFinish && attempt < MaxAttempts && munmap(largeBlock, sz) == 0);
#else
char* largeBlock = (char*)mmap(0, sz, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
#endif