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Make Pals only return amount of memory requested

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The PAL API previously allowed for returning more memory than asked for.
This was when the PAL performed the alignment work, now this is done in
large alloc, so removing from the PAL.
This commit is contained in:
Matthew Parkinson
2020-01-28 14:47:40 +00:00
parent 6e8edefc99
commit 4fea7b8bb1
10 changed files with 27 additions and 37 deletions
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21
src/mem/largealloc.h
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@@ -63,16 +63,11 @@ namespace snmalloc
void new_block()
{
size_t size = SUPERSLAB_SIZE;
void* r = reserve<false>(&size, SUPERSLAB_SIZE);
if (size < SUPERSLAB_SIZE)
error("out of memory");
void* r = reserve<false>(SUPERSLAB_SIZE, SUPERSLAB_SIZE);
PAL::template notify_using<NoZero>(r, OS_PAGE_SIZE);
bump = r;
remaining = size;
remaining = SUPERSLAB_SIZE;
}
/**
@@ -202,7 +197,7 @@ namespace snmalloc
}
template<bool committed>
void* reserve(size_t* size, size_t align) noexcept
void* reserve(size_t size, size_t align) noexcept
{
if constexpr (pal_supports<AlignedAllocation, PAL>)
{
@@ -210,22 +205,20 @@ namespace snmalloc
}
else
{
size_t request = *size;
size_t request = size;
// Add align, so we can guarantee to provide at least size.
request += align;
// Alignment must be a power of 2.
assert(align == bits::next_pow2(align));
void* p = PAL::template reserve<committed>(&request);
void* p = PAL::template reserve<committed>(request);
*size = request;
auto p0 = address_cast(p);
auto start = bits::align_up(p0, align);
if (start > p0)
{
uintptr_t end = bits::align_down(p0 + request, align);
*size = end - start;
PAL::notify_not_using(p, start - p0);
PAL::notify_not_using(pointer_cast<void>(end), (p0 + request) - end);
p = pointer_cast<void>(start);
@@ -302,8 +295,7 @@ namespace snmalloc
if (p == nullptr)
{
size_t add = rsize;
p = memory_provider.template reserve<false>(&add, rsize);
p = memory_provider.template reserve<false>(rsize, rsize);
memory_provider.template notify_using<zero_mem>(p, size);
}
else
@@ -340,6 +332,7 @@ namespace snmalloc
}
}
assert(p == pointer_align_up(p, rsize));
return p;
}