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Subject[PATCH 11/12] percpu: convert chunk hints to be based on pcpu_block_md
Date
As mentioned in the last patch, a chunk's hints are no different than a
block just responsible for more bits. This converts chunk level hints to
use a pcpu_block_md to maintain them. This lets us reuse the same hint
helper functions as a block. The left_free and right_free are unused by
the chunk's pcpu_block_md.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
mm/percpu-internal.h | 5 +-
mm/percpu-stats.c | 5 +-
mm/percpu.c | 120 +++++++++++++++++++------------------------
3 files changed, 57 insertions(+), 73 deletions(-)

diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h
index 119bd1119aa7..0468ba500bd4 100644
--- a/mm/percpu-internal.h
+++ b/mm/percpu-internal.h
@@ -39,9 +39,7 @@ struct pcpu_chunk {

struct list_head list; /* linked to pcpu_slot lists */
int free_bytes; /* free bytes in the chunk */
- int contig_bits; /* max contiguous size hint */
- int contig_bits_start; /* contig_bits starting
- offset */
+ struct pcpu_block_md chunk_md;
void *base_addr; /* base address of this chunk */

unsigned long *alloc_map; /* allocation map */
@@ -49,7 +47,6 @@ struct pcpu_chunk {
struct pcpu_block_md *md_blocks; /* metadata blocks */

void *data; /* chunk data */
- int first_bit; /* no free below this */
bool immutable; /* no [de]population allowed */
int start_offset; /* the overlap with the previous
region to have a page aligned
diff --git a/mm/percpu-stats.c b/mm/percpu-stats.c
index b5fdd43b60c9..ef5034a0464e 100644
--- a/mm/percpu-stats.c
+++ b/mm/percpu-stats.c
@@ -53,6 +53,7 @@ static int find_max_nr_alloc(void)
static void chunk_map_stats(struct seq_file *m, struct pcpu_chunk *chunk,
int *buffer)
{
+ struct pcpu_block_md *chunk_md = &chunk->chunk_md;
int i, last_alloc, as_len, start, end;
int *alloc_sizes, *p;
/* statistics */
@@ -121,9 +122,9 @@ static void chunk_map_stats(struct seq_file *m, struct pcpu_chunk *chunk,
P("nr_alloc", chunk->nr_alloc);
P("max_alloc_size", chunk->max_alloc_size);
P("empty_pop_pages", chunk->nr_empty_pop_pages);
- P("first_bit", chunk->first_bit);
+ P("first_bit", chunk_md->first_free);
P("free_bytes", chunk->free_bytes);
- P("contig_bytes", chunk->contig_bits * PCPU_MIN_ALLOC_SIZE);
+ P("contig_bytes", chunk_md->contig_hint * PCPU_MIN_ALLOC_SIZE);
P("sum_frag", sum_frag);
P("max_frag", max_frag);
P("cur_min_alloc", cur_min_alloc);
diff --git a/mm/percpu.c b/mm/percpu.c
index 7cdf14c242de..197479f2c489 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -233,10 +233,13 @@ static int pcpu_size_to_slot(int size)

static int pcpu_chunk_slot(const struct pcpu_chunk *chunk)
{
- if (chunk->free_bytes < PCPU_MIN_ALLOC_SIZE || chunk->contig_bits == 0)
+ const struct pcpu_block_md *chunk_md = &chunk->chunk_md;
+
+ if (chunk->free_bytes < PCPU_MIN_ALLOC_SIZE ||
+ chunk_md->contig_hint == 0)
return 0;

- return pcpu_size_to_slot(chunk->contig_bits * PCPU_MIN_ALLOC_SIZE);
+ return pcpu_size_to_slot(chunk_md->contig_hint * PCPU_MIN_ALLOC_SIZE);
}

/* set the pointer to a chunk in a page struct */
@@ -592,54 +595,6 @@ static inline bool pcpu_region_overlap(int a, int b, int x, int y)
return false;
}

-/**
- * pcpu_chunk_update - updates the chunk metadata given a free area
- * @chunk: chunk of interest
- * @bit_off: chunk offset
- * @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;
- }
-}
-
-/**
- * pcpu_chunk_refresh_hint - updates metadata about a chunk
- * @chunk: chunk of interest
- *
- * Iterates over the metadata blocks to find the largest contig area.
- * It also counts the populated pages and uses the delta to update the
- * global count.
- *
- * Updates:
- * chunk->contig_bits
- * chunk->contig_bits_start
- */
-static void pcpu_chunk_refresh_hint(struct pcpu_chunk *chunk)
-{
- int bit_off, bits;
-
- /* clear metadata */
- chunk->contig_bits = 0;
-
- bit_off = chunk->first_bit;
- bits = 0;
- pcpu_for_each_md_free_region(chunk, bit_off, bits) {
- pcpu_chunk_update(chunk, bit_off, bits);
- }
-}
-
/**
* pcpu_block_update - updates a block given a free area
* @block: block of interest
@@ -753,6 +708,29 @@ static void pcpu_block_update_scan(struct pcpu_chunk *chunk, int bit_off,
pcpu_block_update(block, s_off, e_off);
}

+/**
+ * pcpu_chunk_refresh_hint - updates metadata about a chunk
+ * @chunk: chunk of interest
+ *
+ * Iterates over the metadata blocks to find the largest contig area.
+ * It also counts the populated pages and uses the delta to update the
+ * global count.
+ */
+static void pcpu_chunk_refresh_hint(struct pcpu_chunk *chunk)
+{
+ struct pcpu_block_md *chunk_md = &chunk->chunk_md;
+ int bit_off, bits;
+
+ /* clear metadata */
+ chunk_md->contig_hint = 0;
+
+ bit_off = chunk_md->first_free;
+ bits = 0;
+ pcpu_for_each_md_free_region(chunk, bit_off, bits) {
+ pcpu_block_update(chunk_md, bit_off, bit_off + bits);
+ }
+}
+
/**
* pcpu_block_refresh_hint
* @chunk: chunk of interest
@@ -800,6 +778,7 @@ static void pcpu_block_refresh_hint(struct pcpu_chunk *chunk, int index)
static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off,
int bits)
{
+ struct pcpu_block_md *chunk_md = &chunk->chunk_md;
int nr_empty_pages = 0;
struct pcpu_block_md *s_block, *e_block, *block;
int s_index, e_index; /* block indexes of the freed allocation */
@@ -910,8 +889,9 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off,
* contig hint is broken. Otherwise, it means a smaller space
* was used and therefore the chunk contig hint is still correct.
*/
- if (pcpu_region_overlap(chunk->contig_bits_start,
- chunk->contig_bits_start + chunk->contig_bits,
+ if (pcpu_region_overlap(chunk_md->contig_hint_start,
+ chunk_md->contig_hint_start +
+ chunk_md->contig_hint,
bit_off,
bit_off + bits))
pcpu_chunk_refresh_hint(chunk);
@@ -930,9 +910,10 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off,
*
* A chunk update is triggered if a page becomes free, a block becomes free,
* or the free spans across blocks. This tradeoff is to minimize iterating
- * over the block metadata to update chunk->contig_bits. chunk->contig_bits
- * may be off by up to a page, but it will never be more than the available
- * space. If the contig hint is contained in one block, it will be accurate.
+ * over the block metadata to update chunk_md->contig_hint.
+ * chunk_md->contig_hint may be off by up to a page, but it will never be more
+ * than the available space. If the contig hint is contained in one block, it
+ * will be accurate.
*/
static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off,
int bits)
@@ -1026,8 +1007,9 @@ static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off,
if (((end - start) >= PCPU_BITMAP_BLOCK_BITS) || s_index != e_index)
pcpu_chunk_refresh_hint(chunk);
else
- pcpu_chunk_update(chunk, pcpu_block_off_to_off(s_index, start),
- end - start);
+ pcpu_block_update(&chunk->chunk_md,
+ pcpu_block_off_to_off(s_index, start),
+ end);
}

/**
@@ -1082,6 +1064,7 @@ static bool pcpu_is_populated(struct pcpu_chunk *chunk, int bit_off, int bits,
static int pcpu_find_block_fit(struct pcpu_chunk *chunk, int alloc_bits,
size_t align, bool pop_only)
{
+ struct pcpu_block_md *chunk_md = &chunk->chunk_md;
int bit_off, bits, next_off;

/*
@@ -1090,12 +1073,12 @@ static int pcpu_find_block_fit(struct pcpu_chunk *chunk, int alloc_bits,
* cannot fit in the global hint, there is memory pressure and creating
* a new chunk would happen soon.
*/
- bit_off = ALIGN(chunk->contig_bits_start, align) -
- chunk->contig_bits_start;
- if (bit_off + alloc_bits > chunk->contig_bits)
+ bit_off = ALIGN(chunk_md->contig_hint_start, align) -
+ chunk_md->contig_hint_start;
+ if (bit_off + alloc_bits > chunk_md->contig_hint)
return -1;

- bit_off = chunk->first_bit;
+ bit_off = chunk_md->first_free;
bits = 0;
pcpu_for_each_fit_region(chunk, alloc_bits, align, bit_off, bits) {
if (!pop_only || pcpu_is_populated(chunk, bit_off, bits,
@@ -1190,6 +1173,7 @@ static unsigned long pcpu_find_zero_area(unsigned long *map,
static int pcpu_alloc_area(struct pcpu_chunk *chunk, int alloc_bits,
size_t align, int start)
{
+ struct pcpu_block_md *chunk_md = &chunk->chunk_md;
size_t align_mask = (align) ? (align - 1) : 0;
unsigned long area_off = 0, area_bits = 0;
int bit_off, end, oslot;
@@ -1222,8 +1206,8 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int alloc_bits,
chunk->free_bytes -= alloc_bits * PCPU_MIN_ALLOC_SIZE;

/* update first free bit */
- if (bit_off == chunk->first_bit)
- chunk->first_bit = find_next_zero_bit(
+ if (bit_off == chunk_md->first_free)
+ chunk_md->first_free = find_next_zero_bit(
chunk->alloc_map,
pcpu_chunk_map_bits(chunk),
bit_off + alloc_bits);
@@ -1245,6 +1229,7 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int alloc_bits,
*/
static void pcpu_free_area(struct pcpu_chunk *chunk, int off)
{
+ struct pcpu_block_md *chunk_md = &chunk->chunk_md;
int bit_off, bits, end, oslot;

lockdep_assert_held(&pcpu_lock);
@@ -1264,7 +1249,7 @@ static void pcpu_free_area(struct pcpu_chunk *chunk, int off)
chunk->free_bytes += bits * PCPU_MIN_ALLOC_SIZE;

/* update first free bit */
- chunk->first_bit = min(chunk->first_bit, bit_off);
+ chunk_md->first_free = min(chunk_md->first_free, bit_off);

pcpu_block_update_hint_free(chunk, bit_off, bits);

@@ -1285,6 +1270,9 @@ static void pcpu_init_md_blocks(struct pcpu_chunk *chunk)
{
struct pcpu_block_md *md_block;

+ /* init the chunk's block */
+ pcpu_init_md_block(&chunk->chunk_md, pcpu_chunk_map_bits(chunk));
+
for (md_block = chunk->md_blocks;
md_block != chunk->md_blocks + pcpu_chunk_nr_blocks(chunk);
md_block++)
@@ -1352,7 +1340,6 @@ static struct pcpu_chunk * __init pcpu_alloc_first_chunk(unsigned long tmp_addr,
chunk->nr_populated = chunk->nr_pages;
chunk->nr_empty_pop_pages = chunk->nr_pages;

- chunk->contig_bits = map_size / PCPU_MIN_ALLOC_SIZE;
chunk->free_bytes = map_size;

if (chunk->start_offset) {
@@ -1362,7 +1349,7 @@ static struct pcpu_chunk * __init pcpu_alloc_first_chunk(unsigned long tmp_addr,
set_bit(0, chunk->bound_map);
set_bit(offset_bits, chunk->bound_map);

- chunk->first_bit = offset_bits;
+ chunk->chunk_md.first_free = offset_bits;

pcpu_block_update_hint_alloc(chunk, 0, offset_bits);
}
@@ -1415,7 +1402,6 @@ static struct pcpu_chunk *pcpu_alloc_chunk(gfp_t gfp)
pcpu_init_md_blocks(chunk);

/* init metadata */
- chunk->contig_bits = region_bits;
chunk->free_bytes = chunk->nr_pages * PAGE_SIZE;

return chunk;
--
2.17.1
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