threads / patch / 60652

patchmem-pool: simplify alignment calculation

Subject: [PATCH] mem-pool: simplify alignment calculation

## tl;dr

One message between Dec 24, 2023 and Dec 24, 2023. Diffs are folded; open one to read it.

replies: 0people: 1as markdown or json

René Scharfe· Dec 24, 2023, 17:02 UTC · lore

Use DIV_ROUND_UP in mem_pool_alloc() to round the allocation length to the next multiple of GIT_MAX_ALIGNMENT instead of twiddling bits explicitly. This is shorter and clearer, to the point that we no longer need the comment that explains what's being calculated.

Signed-off-by: René Scharfe <l.s.r@web.de>
---
Latest Clang emits the same x64 instructions for both versions; GCC only
emits the supposedly optimal output for the patched version:
https://godbolt.org/z/jPscnPqna
 mem-pool.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)
Show changes to mem-pool.c +1 −4
diff --git a/mem-pool.c b/mem-pool.c
index 2b25521e2d..2078c22b09 100644
--- a/mem-pool.c
+++ b/mem-pool.c
@@ -89,9 +89,7 @@ void *mem_pool_alloc(struct mem_pool *pool, size_t len)
 	struct mp_block *p = NULL;
 	void *r;

-	/* round up to a 'GIT_MAX_ALIGNMENT' alignment */
-	if (len & (GIT_MAX_ALIGNMENT - 1))
-		len += GIT_MAX_ALIGNMENT - (len & (GIT_MAX_ALIGNMENT - 1));
+	len = DIV_ROUND_UP(len, GIT_MAX_ALIGNMENT) * GIT_MAX_ALIGNMENT;

 	if (pool->mp_block &&
 	    pool->mp_block->end - pool->mp_block->next_free >= len)
--
2.43.0

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