diff options
| author |   Dennis Zhou <dennis@kernel.org> | 2019-02-13 11:10:30 -0800 |
|---|---|---|
| committer | Dennis Zhou <dennis@kernel.org> | 2019-03-13 12:25:31 -0700 |
| commit | b239f7daf5530f562000bf55f02cc8028703f507 (patch) | |
| tree | 699b64a042de071ada97dc59288d1882181b64b9 /include/linux/percpu.h | |
| parent | percpu: relegate chunks unusable when failing small allocations (diff) | |
| download | linux-dev-b239f7daf5530f562000bf55f02cc8028703f507.tar.xz linux-dev-b239f7daf5530f562000bf55f02cc8028703f507.zip | |
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.h | 12 |
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 >> \ |