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Code Issues Releases Activity

Use heuristic to speed up allocation of small vectors (bug#65491)

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Instead of scanning vector_free_lists from the appropriate size until
we find a nonempty bucket, start at the last bucket where we last put
something in.  This may favour splitting larger vectors than necessary
but in general saves a lot of time in the allocation of small vectors.

Original patch by Ihor Radchenko.

* src/alloc.c (last_inserted_vector_free_idx): New variable.
(setup_on_free_list): Set it.
(allocate_vector_from_block): Use it.
(sweep_vectors): Reset it.
This commit is contained in:
Mattias Engdegård 2023-09-25 17:19:00 +02:00
parent aa28527500
commit 091b8de586
1 changed files with 9 additions and 1 deletions
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10
src/alloc.c
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@ -3155,6 +3155,11 @@ static struct vector_block *vector_blocks;
- For I = VECTOR_FREE_LIST_ARRAY_SIZE-1, VINDEX(BS(V)) ≥ I */
static struct Lisp_Vector *vector_free_lists[VECTOR_FREE_LIST_ARRAY_SIZE];
/* Index to the bucket in vector_free_lists into which we last inserted
or split a free vector. We use this as a heuristic telling us where
to start looking for free vectors when the exact-size bucket is empty. */
static ptrdiff_t last_inserted_vector_free_idx = VECTOR_FREE_LIST_ARRAY_SIZE;
/* Singly-linked list of large vectors. */
static struct large_vector *large_vectors;
@ -3191,6 +3196,7 @@ setup_on_free_list (struct Lisp_Vector *v, ptrdiff_t nbytes)
set_next_vector (v, vector_free_lists[vindex]);
ASAN_POISON_VECTOR_CONTENTS (v, nbytes - header_size);
vector_free_lists[vindex] = v;
last_inserted_vector_free_idx = vindex;
}
/* Get a new vector block. */
@ -3256,7 +3262,8 @@ allocate_vector_from_block (ptrdiff_t nbytes)
/* Next, check free lists containing larger vectors. Since
we will split the result, we should have remaining space
large enough to use for one-slot vector at least. */
for (index = VINDEX (nbytes + VBLOCK_BYTES_MIN);
for (index = max (VINDEX (nbytes + VBLOCK_BYTES_MIN),
last_inserted_vector_free_idx);
index < VECTOR_FREE_LIST_ARRAY_SIZE; index++)
if (vector_free_lists[index])
{
@ -3489,6 +3496,7 @@ sweep_vectors (void)
gcstat.total_vectors = 0;
gcstat.total_vector_slots = gcstat.total_free_vector_slots = 0;
memset (vector_free_lists, 0, sizeof (vector_free_lists));
last_inserted_vector_free_idx = VECTOR_FREE_LIST_ARRAY_SIZE;
/* Looking through vector blocks. */