support page size that are not power of two - #4854
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Pull request overview
This PR updates TurboMind’s internal memory allocators so the page size no longer needs to be a power of two, and plumbs a configurable page_size from ObjectAllocator down into PageAllocator/SlabAllocator.
Changes:
- Add power-of-two detection and a modulo/division fallback path in
PageAllocatorfor base alignment and page indexing. - Update slab sizing to derive from
page_size(instead of a fixed minimum slab size) and prevent growing slabs pastmax_size. - Add a new
ObjectAllocator(Buffer, size_t page_size)overload and route the default constructor through it.
Reviewed changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.
| File | Description |
|---|---|
src/turbomind/memory/slab.h |
Changes slab size derivation to use page_size and adjusts the growth cap condition. |
src/turbomind/memory/page.h |
Introduces is_power_of_2 and non-power-of-two-safe alignment/indexing/page-count logic. |
src/turbomind/memory/object.h |
Adds a new public constructor overload that accepts page_size. |
src/turbomind/memory/object.cc |
Threads page_size into MemoryState/SlabAllocator and implements the new constructor overload. |
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| // the smallest page_count needed to hold an object | ||
| int page_count = static_cast<int>((object_size + page_size - 1) / page_size); | ||
| size_t size = static_cast<size_t>(ceil_pow2(page_count)) * page_size; | ||
|
|
| // double slab size until utilization >= threshold | ||
| float ratio = get_ratio(size); | ||
| while (ratio < threshold && size < max_size) { | ||
| while (ratio < threshold && size * 2 <= max_size) { |
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| page_size_{page_size}, | ||
| is_page_size_pow2_{is_power_of_2(page_size)}, | ||
| page_size_log2_{ceil_log2(page_size)}, | ||
| pages_{static_cast<int>(size_ / page_size)}, // | ||
| max_order_{ceil_log2(pages_)}, |
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| ObjectAllocator::ObjectAllocator(Buffer region, size_t page_size): | ||
| impl_{std::make_unique<Impl>(std::move(region), page_size)} | ||
| { | ||
| } |
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| if (is_power_of_2(page_size)) { | ||
| const auto mask = static_cast<uintptr_t>(page_size) - 1; | ||
| return reinterpret_cast<char*>((p + mask) & ~mask); | ||
| } | ||
| const auto remainder = p % page_size; |
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