percpu: set PCPU_BITMAP_BLOCK_SIZE to PAGE_SIZE
Previously, block size was flexible based on the constraint that the
GCD(PCPU_BITMAP_BLOCK_SIZE, PAGE_SIZE) > 1. However, this carried the
overhead that keeping a floating number of populated free pages required
scanning over the free regions of a chunk.
Setting the block size to be fixed at PAGE_SIZE lets us know when an
empty page becomes used as we will break a full contig_hint of a block.
This means we no longer have to scan the whole chunk upon breaking a
contig_hint which empty page management piggybacked off. A later patch
takes advantage of this to optimize the allocation path by only scanning
forward using the scan_hint introduced later too.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
diff --git a/mm/percpu-km.c b/mm/percpu-km.c
index b68d5df..3a2ff5c 100644
--- a/mm/percpu-km.c
+++ b/mm/percpu-km.c
@@ -70,7 +70,7 @@
chunk->base_addr = page_address(pages);
spin_lock_irqsave(&pcpu_lock, flags);
- pcpu_chunk_populated(chunk, 0, nr_pages, false);
+ pcpu_chunk_populated(chunk, 0, nr_pages);
spin_unlock_irqrestore(&pcpu_lock, flags);
pcpu_stats_chunk_alloc();