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authorDennis Zhou (Facebook) <dennisszhou@gmail.com>2017-07-24 19:02:15 -0400
committerTejun Heo <tj@kernel.org>2017-07-26 17:41:05 -0400
commit268625a6f9df6a7c9b0ae7707a8a1cd5a9993bd2 (patch)
tree4f178b5e62a183be1c23a5d058c6eecedbfd67d5 /mm/percpu.c
parent13f966373f9296c0da2fb2764654cce520b3a6b4 (diff)
download96b-common-268625a6f9df6a7c9b0ae7707a8a1cd5a9993bd2.tar.gz
percpu: keep track of the best offset for contig hints
This patch makes the contig hint starting offset optimization from the previous patch as honest as it can be. For both chunk and block starting offsets, make sure it keeps the starting offset with the best alignment. The block skip optimization is added in a later patch when the pcpu_find_block_fit iterator is swapped in. Signed-off-by: Dennis Zhou <dennisszhou@gmail.com> Reviewed-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'mm/percpu.c')
-rw-r--r--mm/percpu.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/mm/percpu.c b/mm/percpu.c
index 734745a0c9b6..d0d3fa872a8c 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -401,12 +401,18 @@ static inline int pcpu_cnt_pop_pages(struct pcpu_chunk *chunk, int bit_off,
* @bits: size of free area
*
* This updates the chunk's contig hint and starting offset given a free area.
+ * Choose the best starting offset if the contig hint is equal.
*/
static void pcpu_chunk_update(struct pcpu_chunk *chunk, int bit_off, int bits)
{
if (bits > chunk->contig_bits) {
chunk->contig_bits_start = bit_off;
chunk->contig_bits = bits;
+ } else if (bits == chunk->contig_bits && chunk->contig_bits_start &&
+ (!bit_off ||
+ __ffs(bit_off) > __ffs(chunk->contig_bits_start))) {
+ /* use the start with the best alignment */
+ chunk->contig_bits_start = bit_off;
}
}
@@ -461,7 +467,8 @@ static void pcpu_chunk_refresh_hint(struct pcpu_chunk *chunk)
* @end: end offset in block
*
* Updates a block given a known free area. The region [start, end) is
- * expected to be the entirety of the free area within a block.
+ * expected to be the entirety of the free area within a block. Chooses
+ * the best starting offset if the contig hints are equal.
*/
static void pcpu_block_update(struct pcpu_block_md *block, int start, int end)
{
@@ -477,6 +484,10 @@ static void pcpu_block_update(struct pcpu_block_md *block, int start, int end)
if (contig > block->contig_hint) {
block->contig_hint_start = start;
block->contig_hint = contig;
+ } else if (block->contig_hint_start && contig == block->contig_hint &&
+ (!start || __ffs(start) > __ffs(block->contig_hint_start))) {
+ /* use the start with the best alignment */
+ block->contig_hint_start = start;
}
}