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largealloc: don't zero memory twice

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If the decommit strategy is DecommitSuperLazy, then both the constexpr
if and the ordinary if would fire; add an else so we only fall into one.
This commit is contained in:
Nathaniel Filardo
2019-05-20 13:23:51 +01:00
parent 6f8623b5d7
commit ad96ba05c1
2 changed files with 10 additions and 24 deletions
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1
src/mem/alloc.h
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@@ -1263,6 +1263,7 @@ namespace snmalloc
stats().large_dealloc(large_class);
// Cross-reference largealloc's alloc() decommitted condition.
if ((decommit_strategy != DecommitNone) || (large_class > 0))
large_allocator.memory_provider.notify_not_using(
pointer_offset(p, OS_PAGE_SIZE), rsize - OS_PAGE_SIZE);

33
src/mem/largealloc.h
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@@ -344,30 +344,14 @@ namespace snmalloc
{
stats.superslab_pop();
if constexpr (decommit_strategy == DecommitSuperLazy)
{
if (static_cast<Baseslab*>(p)->get_kind() == Decommitted)
{
// The first page is already in "use" for the stack element,
// this will need zeroing for a YesZero call.
if constexpr (zero_mem == YesZero)
memory_provider.template zero<true>(p, OS_PAGE_SIZE);
// Cross-reference alloc.h's large_dealloc decommitment condition
// and lazy_decommit_if_needed.
bool decommitted =
((decommit_strategy == DecommitSuperLazy) &&
(static_cast<Baseslab*>(p)->get_kind() == Decommitted)) ||
(large_class > 0) || (decommit_strategy != DecommitNone);
// Notify we are using the rest of the allocation.
// Passing zero_mem ensures the PAL provides zeroed pages if
// required.
memory_provider.template notify_using<zero_mem>(
pointer_offset(p, OS_PAGE_SIZE),
bits::align_up(size, OS_PAGE_SIZE) - OS_PAGE_SIZE);
}
else
{
if constexpr (zero_mem == YesZero)
memory_provider.template zero<true>(
p, bits::align_up(size, OS_PAGE_SIZE));
}
}
if ((decommit_strategy != DecommitNone) || (large_class > 0))
if (decommitted)
{
// The first page is already in "use" for the stack element,
// this will need zeroing for a YesZero call.
@@ -375,7 +359,8 @@ namespace snmalloc
memory_provider.template zero<true>(p, OS_PAGE_SIZE);
// Notify we are using the rest of the allocation.
// Passing zero_mem ensures the PAL provides zeroed pages if required.
// Passing zero_mem ensures the PAL provides zeroed pages if
// required.
memory_provider.template notify_using<zero_mem>(
pointer_offset(p, OS_PAGE_SIZE),
bits::align_up(size, OS_PAGE_SIZE) - OS_PAGE_SIZE);