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authorDennis Zhou <dennis@kernel.org>2019-02-13 22:10:30 +0300
committerDennis Zhou <dennis@kernel.org>2019-03-13 22:25:31 +0300
commitb239f7daf5530f562000bf55f02cc8028703f507 (patch)
tree699b64a042de071ada97dc59288d1882181b64b9 /include/linux/percpu.h
parent8744d859427c6198dce490619809754336954297 (diff)
downloadlinux-b239f7daf5530f562000bf55f02cc8028703f507.tar.xz
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>
Diffstat (limited to 'include/linux/percpu.h')
-rw-r--r--include/linux/percpu.h12
1 files changed, 3 insertions, 9 deletions
diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index 70b7123f38c7..9909dc0e273a 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -26,16 +26,10 @@
#define PCPU_MIN_ALLOC_SHIFT 2
#define PCPU_MIN_ALLOC_SIZE (1 << PCPU_MIN_ALLOC_SHIFT)
-/* number of bits per page, used to trigger a scan if blocks are > PAGE_SIZE */
-#define PCPU_BITS_PER_PAGE (PAGE_SIZE >> PCPU_MIN_ALLOC_SHIFT)
-
/*
- * This determines the size of each metadata block. There are several subtle
- * constraints around this constant. The reserved region must be a multiple of
- * PCPU_BITMAP_BLOCK_SIZE. Additionally, PCPU_BITMAP_BLOCK_SIZE must be a
- * multiple of PAGE_SIZE or PAGE_SIZE must be a multiple of
- * PCPU_BITMAP_BLOCK_SIZE to align with the populated page map. The unit_size
- * also has to be a multiple of PCPU_BITMAP_BLOCK_SIZE to ensure full blocks.
+ * The PCPU_BITMAP_BLOCK_SIZE must be the same size as PAGE_SIZE as the
+ * updating of hints is used to manage the nr_empty_pop_pages in both
+ * the chunk and globally.
*/
#define PCPU_BITMAP_BLOCK_SIZE PAGE_SIZE
#define PCPU_BITMAP_BLOCK_BITS (PCPU_BITMAP_BLOCK_SIZE >> \