[PATCH 14/17] mm/percpu: micro-optimize pcpu_is_populated()
From: Yury Norov <yury.norov@gmail.com>
Date: 2021-08-14 21:20:22
Also in:
kvm, linux-arch, linux-kselftest, linux-mm, linux-mmc, lkml
Subsystem:
memory management, per-cpu memory allocator, the rest · Maintainers:
Andrew Morton, Dennis Zhou, Tejun Heo, Christoph Lameter, Linus Torvalds
bitmap_next_clear_region() calls find_next_zero_bit() and find_next_bit() sequentially to find a range of clear bits. In case of pcpu_is_populated() there's a chance to return earlier if bitmap has all bits set. Signed-off-by: Yury Norov <yury.norov@gmail.com> Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Acked-by: Dennis Zhou <dennis@kernel.org> --- mm/percpu.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/mm/percpu.c b/mm/percpu.c
index a43039629aa4..8bf8b88446d7 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c@@ -1070,17 +1070,18 @@ static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off, static bool pcpu_is_populated(struct pcpu_chunk *chunk, int bit_off, int bits, int *next_off) { - unsigned int page_start, page_end, rs, re; + unsigned int start, end; - page_start = PFN_DOWN(bit_off * PCPU_MIN_ALLOC_SIZE); - page_end = PFN_UP((bit_off + bits) * PCPU_MIN_ALLOC_SIZE); + start = PFN_DOWN(bit_off * PCPU_MIN_ALLOC_SIZE); + end = PFN_UP((bit_off + bits) * PCPU_MIN_ALLOC_SIZE); - rs = page_start; - bitmap_next_clear_region(chunk->populated, &rs, &re, page_end); - if (rs >= page_end) + start = find_next_zero_bit(chunk->populated, end, start); + if (start >= end) return true; - *next_off = re * PAGE_SIZE / PCPU_MIN_ALLOC_SIZE; + end = find_next_bit(chunk->populated, end, start + 1); + + *next_off = end * PAGE_SIZE / PCPU_MIN_ALLOC_SIZE; return false; }
--
2.30.2