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commit 36e56e9d37ac24d160b50a6f564c88d8df75c8da Author: Marco Casaroli <[email protected]> AuthorDate: Thu Oct 29 18:56:46 2026 +0100 mm/mm_gran: Start the search at the lowest free granule. The search still read each word of the table below the first free granule. With 20000 used granules, a search for one granule read 625 words. Keep the position of the lowest free granule in struct gran_s (lowfree). gran_set() moves it up when an allocation takes that granule, and gran_clear() moves it down when a lower granule becomes free. gran_search() starts at lowfree. The result does not change, because no granule below lowfree is free. In a host test with 20000 used granules, one search for one granule takes 2 ns, not 178 ns. Assisted-by: Claude Code:claude-opus-5-5 Signed-off-by: Marco Casaroli <[email protected]> --- mm/mm_gran/mm_gran.h | 1 + mm/mm_gran/mm_grantable.c | 17 ++++++++++++++++- 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/mm/mm_gran/mm_gran.h b/mm/mm_gran/mm_gran.h index c56e1f517ff..7738b08fd74 100644 --- a/mm/mm_gran/mm_gran.h +++ b/mm/mm_gran/mm_gran.h @@ -70,6 +70,7 @@ struct gran_s uint8_t log2gran; /* Log base 2 of the size of one granule */ uint8_t log2align; /* Log base 2 of required alignment */ uint32_t ngranules; /* The total number of (aligned) granules in the heap */ + uint32_t lowfree; /* No granule below this one is free */ #ifdef CONFIG_GRAN_INTR irqstate_t irqstate; /* For exclusive access to the GAT */ spinlock_t lock; diff --git a/mm/mm_gran/mm_grantable.c b/mm/mm_gran/mm_grantable.c index 1ebb0047d43..9194edcd6f8 100644 --- a/mm/mm_gran/mm_grantable.c +++ b/mm/mm_gran/mm_grantable.c @@ -296,7 +296,7 @@ failure: int gran_search(const gran_t *gran, size_t size) { - size_t posi = 0; + size_t posi; size_t used; if (gran == NULL || gran->ngranules < size) @@ -304,6 +304,9 @@ int gran_search(const gran_t *gran, size_t size) return -EINVAL; } + /* No granule below lowfree is free: start there */ + + posi = gran->lowfree; for (; ; ) { /* The first free granule, then the first used one after it */ @@ -334,6 +337,13 @@ int gran_set(gran_t *gran, size_t posi, size_t size) if (ret == OK) { gran_set_(gran, &rang, true); + + /* The range took the lowest free granule: the next one is above it */ + + if (gran->lowfree >= posi && gran->lowfree < posi + size) + { + gran->lowfree = posi + size; + } } return ret; @@ -349,6 +359,11 @@ int gran_clear(gran_t *gran, size_t posi, size_t size) if (ret == OK) { gran_set_(gran, &rang, false); + + if (posi < gran->lowfree) + { + gran->lowfree = posi; + } } return ret;
