xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

percpu: set PCPU_BITMAP_BLOCK_SIZE to PAGE_SIZE

Browse Source 
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>
This commit is contained in:
Dennis Zhou
2019-02-13 11:10:30 -08:00
parent 8744d85942
commit b239f7daf5
3 changed files with 48 additions and 76 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
include/linux/percpu.h
View File

@@ -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 >> \