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Return the original block when a multiple mempool realloc request still fits in the current pool block. This avoids unnecessary allocation, copy, and free work for same size class reallocations. Signed-off-by: chao an <anchao.archer@bytedance.com>
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Area: Memory Management
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| (((FAR char *)kasan_clear_tag(oldblk) - | ||
| ((FAR char *)kasan_clear_tag(dict->addr) + | ||
| mpool->minpoolsize)) % MEMPOOL_REALBLOCKSIZE(dict->pool)); | ||
| if (size > 0 && size <= dict->pool->blocksize && blkbase == oldblk) |
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why need check blkbase == oldblk
casaroli
requested changes
Oct 27, 2026
| (((FAR char *)kasan_clear_tag(oldblk) - | ||
| ((FAR char *)kasan_clear_tag(dict->addr) + | ||
| mpool->minpoolsize)) % MEMPOOL_REALBLOCKSIZE(dict->pool)); | ||
| if (size > 0 && size <= dict->pool->blocksize && blkbase == oldblk) |
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This also keeps the block when the size shrinks to a smaller pool: realloc(p, 16) on a 512-byte block now keeps the 512-byte block, where before the data moved to the 16-byte pool.
Fix: reuse the block only when mempool_multiple_find(mpool, size) == dict->pool.
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Summary
Optimize
mempool_multiple_realloc()by returning the original block whenthe requested size still fits in the current multiple mempool block.
The previous implementation always allocated a new block, copied data, and
freed the old block even when the new size stayed within the same pool size
class. This change adds an in-place fast path for normal mempool blocks.
Details
The fast path is used only when:
The base-address check keeps existing behavior for interior pointers such as
mempool_multiple_memalign()results, where the available tail space may besmaller than the full pool block.
Benefits
Testing
sim/nsh