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AK+Kernel: Avoid double memory clearing of HashTable buckets
Since the allocated memory is going to be zeroed immediately anyway, let's avoid redundantly scrubbing it with MALLOC_SCRUB_BYTE just before that. The latest versions of gcc and Clang can automatically do this malloc + memset -> calloc optimization, but I've seen a couple of places where it failed to be done. This commit also adds a naive kcalloc function to the kernel that doesn't (yet) eliminate the redundancy like the userland does.
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e3eb68dd58
Notes:
sideshowbarker
2024-07-17 17:23:55 +09:00
Author: https://github.com/BertalanD Commit: https://github.com/SerenityOS/serenity/commit/e3eb68dd58 Pull-request: https://github.com/SerenityOS/serenity/pull/13051
@ -461,12 +461,11 @@ private:
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auto old_capacity = m_capacity;
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Iterator old_iter = begin();
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auto* new_buckets = kmalloc(size_in_bytes(new_capacity));
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auto* new_buckets = kcalloc(1, size_in_bytes(new_capacity));
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if (!new_buckets)
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return Error::from_errno(ENOMEM);
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m_buckets = (BucketType*)new_buckets;
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__builtin_memset(m_buckets, 0, size_in_bytes(new_capacity));
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m_capacity = new_capacity;
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m_deleted_count = 0;
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@ -15,6 +15,7 @@
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# include <new>
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# include <stdlib.h>
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# define kcalloc calloc
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# define kmalloc malloc
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# define kmalloc_good_size malloc_good_size
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@ -449,6 +449,18 @@ void* kmalloc(size_t size)
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return ptr;
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}
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void* kcalloc(size_t count, size_t size)
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{
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if (Checked<size_t>::multiplication_would_overflow(count, size))
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return nullptr;
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size_t new_size = count * size;
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auto* ptr = kmalloc(new_size);
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// FIXME: Avoid redundantly scrubbing the memory in kmalloc()
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if (ptr)
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memset(ptr, 0, new_size);
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return ptr;
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}
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void kfree_sized(void* ptr, size_t size)
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{
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if (!ptr)
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@ -72,6 +72,7 @@ void operator delete[](void* ptrs) noexcept DISALLOW("All deletes in the kernel
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void operator delete[](void* ptr, size_t) noexcept;
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[[gnu::malloc, gnu::alloc_size(1)]] void* kmalloc(size_t);
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[[gnu::malloc, gnu::alloc_size(1, 2)]] void* kcalloc(size_t, size_t);
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[[gnu::malloc, gnu::alloc_size(1), gnu::alloc_align(2)]] void* kmalloc_aligned(size_t size, size_t alignment);
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