[kernel] E: Batch page allocation in ELF loader#16
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Restructure the ELF segment loader to batch-allocate contiguous page runs instead of allocating one page at a time via alloc_upages(1). Pages within each segment are grouped by their clear requirement (data pages that will be overwritten vs BSS pages that must be zeroed) and each contiguous run is allocated with a single alloc_upages(nframes) call. This reduces the number of frame-allocator and page-table operations from O(pages) to O(runs), typically 2-3 per segment (one for the data region and one for the BSS region). To support large batch sizes without exhausting the 128 KB kernel slab, alloc_upages is refactored to process frames in fixed-size chunks (MAX_CHUNK = 32). Each chunk allocates a small Vec that is dropped before the next chunk begins. A rollback helper and a free_remaining_frames helper ensure that both mapped pages and unprocessed frames are properly cleaned up on error. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Replica of nanvix#2042.
Summary
Batch page allocation in the ELF segment loader and chunk-based processing in alloc_upages to reduce the cost of loading large ELF binaries.
Problem
The ELF loader allocates every page individually. For a ~14 MB binary like Python 3.12 (~3,584 pages), this results in ~3,584 separate frame-allocator + page-table operations.
Changes
ELF segment allocation (elf.rs)
Phase 1: Collect contiguous runs of unmapped pages, allocate each run with a single alloc_upages(nframes) call.
Phase 2: Copy segment data into allocated pages.
Chunked alloc_upages (manager.rs)
Process frames in fixed-size chunks (MAX_CHUNK = 32). Improved error handling with rollback_mapped_pages and free_remaining_frames.
Benchmark (Python 3.12 hello world, WHP standalone)