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Revert "[scudo] Fix the logic of MaxAllowedFragmentedPages" (#108130)

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Reverts llvm/llvm-project#107927

We are supposed to check the MaxAllowedFragmentedPages instead.
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ChiaHungDuan 2024-09-10 18:56:49 -07:00 committed by GitHub
parent 5773adb0bf
commit 76151c4490
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1 changed files with 8 additions and 17 deletions
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compiler-rt/lib/scudo/standalone/secondary.h
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@ -72,16 +72,13 @@ namespace {
struct CachedBlock {
static constexpr u16 CacheIndexMax = UINT16_MAX;
static constexpr u16 InvalidEntry = CacheIndexMax;
// We allow a certain amount of fragmentation and part of the fragmented bytes
// will be released by `releaseAndZeroPagesToOS()`. This increases the chance
// of cache hit rate and reduces the overhead to the RSS at the same time. See
// more details in the `MapAllocatorCache::retrieve()` section.
//
// We arrived at this default value after noticing that mapping in larger
// memory regions performs better than releasing memory and forcing a cache
// hit. According to the data, it suggests that beyond 4 pages, the release
// execution time is longer than the map execution time. In this way,
// the default is dependent on the platform.
// * MaxReleasedCachePages default is currently 4
// - We arrived at this value after noticing that mapping
// in larger memory regions performs better than releasing
// memory and forcing a cache hit. According to the data,
// it suggests that beyond 4 pages, the release execution time is
// longer than the map execution time. In this way, the default
// is dependent on the platform.
static constexpr uptr MaxReleasedCachePages = 4U;
uptr CommitBase = 0;
@ -728,14 +725,8 @@ MapAllocator<Config>::tryAllocateFromCache(const Options &Options, uptr Size,
uptr EntryHeaderPos;
uptr MaxAllowedFragmentedPages = MaxUnreleasedCachePages;
if (LIKELY(!useMemoryTagging<Config>(Options))) {
if (UNLIKELY(useMemoryTagging<Config>(Options)))
MaxAllowedFragmentedPages += CachedBlock::MaxReleasedCachePages;
} else {
// TODO: Enable MaxReleasedCachePages may result in pages for an entry being
// partially released and it erases the tag of those pages as well. To
// support this feature for MTE, we need to tag those pages again.
DCHECK_EQ(CachedBlock::MaxReleasedCachePages, 0U);
}
Entry = Cache.retrieve(MaxAllowedFragmentedPages, Size, Alignment,
getHeadersSize(), EntryHeaderPos);