The new struct is introduced to prevent mis-use of hint start and size and improve readability. Link: https://lore.kernel.org/all/aegQgyf3KuIZMK9x@palisades.local/ Suggested-by: Dennis Zhou Signed-off-by: Joonwon Kang --- v6: No change. v5: Add missing change for mm/percpu-stats.c. v4: Initial version. mm/percpu-internal.h | 24 +++-- mm/percpu-stats.c | 2 +- mm/percpu.c | 244 ++++++++++++++++++++----------------------- 3 files changed, 131 insertions(+), 139 deletions(-) diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h index 4b3d6ec43703..dd95ec2c243a 100644 --- a/mm/percpu-internal.h +++ b/mm/percpu-internal.h @@ -6,6 +6,15 @@ #include #include +/* + * pcpu region represents a hint region. + * A region is only valid when @size is greater than 0. + */ +struct pcpu_region { + int start; + int size; +}; + /* * pcpu_block_md is the metadata block struct. * Each chunk's bitmap is split into a number of full blocks. @@ -13,17 +22,14 @@ * * The scan hint is the largest known contiguous area before the contig hint. * It is not necessarily the actual largest contig hint though. There is an - * invariant that the scan_hint_start > contig_hint_start iff - * scan_hint == contig_hint. This is necessary because when scanning forward, - * we don't know if a new contig hint would be better than the current one. + * invariant that the scan_hint.start > contig_hint.start iff + * scan_hint.size == contig_hint.size. This is necessary because when scanning + * forward, we don't know if a new contig hint would be better than the current + * one. */ struct pcpu_block_md { - int scan_hint; /* scan hint for block */ - int scan_hint_start; /* block relative starting - position of the scan hint */ - int contig_hint; /* contig hint for block */ - int contig_hint_start; /* block relative starting - position of the contig hint */ + struct pcpu_region scan_hint; /* scan hint for block */ + struct pcpu_region contig_hint; /* contig hint for block */ int left_free; /* size of free space along the left side of the block */ int right_free; /* size of free space along diff --git a/mm/percpu-stats.c b/mm/percpu-stats.c index 9b9d5d6accae..4a735d09adef 100644 --- a/mm/percpu-stats.c +++ b/mm/percpu-stats.c @@ -122,7 +122,7 @@ static void chunk_map_stats(struct seq_file *m, struct pcpu_chunk *chunk, P("empty_pop_pages", chunk->nr_empty_pop_pages); P("first_bit", chunk_md->first_free); P("free_bytes", chunk->free_bytes); - P("contig_bytes", chunk_md->contig_hint * PCPU_MIN_ALLOC_SIZE); + P("contig_bytes", chunk_md->contig_hint.size * 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 0f6dd5260f56..89b7f33500cf 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -244,10 +244,11 @@ static int pcpu_chunk_slot(const struct pcpu_chunk *chunk) const struct pcpu_block_md *chunk_md = &chunk->chunk_md; if (chunk->free_bytes < PCPU_MIN_ALLOC_SIZE || - chunk_md->contig_hint == 0) + chunk_md->contig_hint.size == 0) return 0; - return pcpu_size_to_slot(chunk_md->contig_hint * PCPU_MIN_ALLOC_SIZE); + return pcpu_size_to_slot(chunk_md->contig_hint.size * + PCPU_MIN_ALLOC_SIZE); } /* set the pointer to a chunk in a page struct */ @@ -317,10 +318,10 @@ static unsigned long pcpu_block_off_to_off(int index, int off) static bool pcpu_check_block_hint(struct pcpu_block_md *block, int bits, size_t align) { - int bit_off = ALIGN(block->contig_hint_start, align) - - block->contig_hint_start; + int bit_off = ALIGN(block->contig_hint.start, align) - + block->contig_hint.start; - return bit_off + bits <= block->contig_hint; + return bit_off + bits <= block->contig_hint.size; } /* @@ -330,7 +331,7 @@ static bool pcpu_check_block_hint(struct pcpu_block_md *block, int bits, * * This determines if we should scan based on the scan_hint or first_free. * In general, we want to scan from first_free to fulfill allocations by - * first fit. However, if we know a scan_hint at position scan_hint_start + * first fit. However, if we know a scan_hint at position scan_hint.start * cannot fulfill an allocation, we can begin scanning from there knowing * the contig_hint will be our fallback. */ @@ -340,13 +341,13 @@ static int pcpu_next_hint(struct pcpu_block_md *block, int alloc_bits) * The three conditions below determine if we can skip past the * scan_hint. First, does the scan hint exist. Second, is the * contig_hint after the scan_hint (possibly not true iff - * contig_hint == scan_hint). Third, is the allocation request - * larger than the scan_hint. + * contig_hint.size == scan_hint.size). Third, is the allocation + * request larger than the scan_hint. */ - if (block->scan_hint && - block->contig_hint_start > block->scan_hint_start && - alloc_bits > block->scan_hint) - return block->scan_hint_start + block->scan_hint; + if (block->scan_hint.size && + block->contig_hint.start > block->scan_hint.start && + alloc_bits > block->scan_hint.size) + return block->scan_hint.start + block->scan_hint.size; return block->first_free; } @@ -388,11 +389,11 @@ static void pcpu_next_md_free_region(struct pcpu_chunk *chunk, int *bit_off, * the next block and should be handled by the contig area * across blocks code. */ - *bits = block->contig_hint; - if (*bits && block->contig_hint_start >= block_off && - *bits + block->contig_hint_start < PCPU_BITMAP_BLOCK_BITS) { + *bits = block->contig_hint.size; + if (*bits && block->contig_hint.start >= block_off && + *bits + block->contig_hint.start < PCPU_BITMAP_BLOCK_BITS) { *bit_off = pcpu_block_off_to_off(i, - block->contig_hint_start); + block->contig_hint.start); return; } /* reset to satisfy the second predicate above */ @@ -437,19 +438,18 @@ static void pcpu_next_fit_region(struct pcpu_chunk *chunk, int alloc_bits, } /* check block->contig_hint */ - *bits = ALIGN(block->contig_hint_start, align) - - block->contig_hint_start; + *bits = ALIGN(block->contig_hint.start, align) - + block->contig_hint.start; /* * This uses the block offset to determine if this has been * checked in the prior iteration. */ - if (block->contig_hint && - block->contig_hint_start >= block_off && - block->contig_hint >= *bits + alloc_bits) { + if (block->contig_hint.size && + block->contig_hint.start >= block_off && + block->contig_hint.size >= *bits + alloc_bits) { int start = pcpu_next_hint(block, alloc_bits); - *bits += alloc_bits + block->contig_hint_start - - start; + *bits += alloc_bits + block->contig_hint.start - start; *bit_off = pcpu_block_off_to_off(i, start); return; } @@ -604,17 +604,16 @@ static inline void pcpu_update_empty_pages(struct pcpu_chunk *chunk, int nr) /* * pcpu_region_overlap - determines if two regions overlap - * @a: start of first region, inclusive - * @b: end of first region, exclusive - * @x: start of second region, inclusive - * @y: end of second region, exclusive + * @a: first region + * @b: second region * - * This is used to determine if the hint region [a, b) overlaps with the - * allocated region [x, y). + * This is used to determine if the hint region [a.start, a.start + a.size) + * overlaps with the allocated region [b.start, b.start + b.size). */ -static inline bool pcpu_region_overlap(int a, int b, int x, int y) +static inline bool pcpu_region_overlap(struct pcpu_region a, + struct pcpu_region b) { - return (a < y) && (x < b); + return (a.start < b.start + b.size) && (b.start < a.start + a.size); } /** @@ -629,56 +628,54 @@ static inline bool pcpu_region_overlap(int a, int b, int x, int y) */ static void pcpu_block_update(struct pcpu_block_md *block, int start, int end) { - int contig = end - start; + struct pcpu_region free = { .start = start, .size = end - start }; - block->first_free = min(block->first_free, start); - if (start == 0) - block->left_free = contig; + block->first_free = min(block->first_free, free.start); + if (free.start == 0) + block->left_free = free.size; - if (end == block->nr_bits) - block->right_free = contig; + if (free.start + free.size == block->nr_bits) + block->right_free = free.size; - if (contig > block->contig_hint) { + if (free.size > block->contig_hint.size) { /* promote the old contig_hint to be the new scan_hint */ - if (block->contig_hint && start > block->contig_hint_start) { - if (block->contig_hint > block->scan_hint) { - block->scan_hint_start = - block->contig_hint_start; + if (block->contig_hint.size && + free.start > block->contig_hint.start) { + if (block->contig_hint.size > block->scan_hint.size) { block->scan_hint = block->contig_hint; - } else if (block->scan_hint && - start < block->scan_hint_start) { + } else if (block->scan_hint.size && + free.start < block->scan_hint.start) { /* - * The old contig_hint == scan_hint. But, the - * new contig is larger so hold the invariant - * scan_hint_start < contig_hint_start. + * The old contig_hint.size == scan_hint.size. + * But, the new contig is larger so hold the + * invariant scan_hint.start < + * contig_hint.start. */ - block->scan_hint = 0; + block->scan_hint.size = 0; } } else { - block->scan_hint = 0; + block->scan_hint.size = 0; } - block->contig_hint_start = start; - block->contig_hint = contig; - } else if (contig == block->contig_hint) { - if (block->contig_hint_start && - (!start || - __ffs(start) > __ffs(block->contig_hint_start))) { - /* start has a better alignment so use it */ - block->contig_hint_start = start; - if (block->scan_hint && - start < block->scan_hint_start && - block->contig_hint > block->scan_hint) - block->scan_hint = 0; - } else if ((block->scan_hint && - start > block->scan_hint_start) || - block->contig_hint > block->scan_hint) { + block->contig_hint = free; + } else if (free.size == block->contig_hint.size) { + if (block->contig_hint.start && + (!free.start || + __ffs(free.start) > __ffs(block->contig_hint.start))) { + /* new start has a better alignment so use it */ + block->contig_hint.start = free.start; + if (block->scan_hint.size && + free.start < block->scan_hint.start && + block->contig_hint.size > block->scan_hint.size) + block->scan_hint.size = 0; + } else if ((block->scan_hint.size && + free.start > block->scan_hint.start) || + block->contig_hint.size > block->scan_hint.size) { /* - * Knowing contig == contig_hint, update the scan_hint - * if it is farther than or larger than the current - * scan_hint. + * Knowing new contig size == contig_hint.size, update + * the scan_hint if it is farther than or larger than + * the current scan_hint. */ - block->scan_hint_start = start; - block->scan_hint = contig; + block->scan_hint = free; } } else { /* @@ -686,12 +683,11 @@ static void pcpu_block_update(struct pcpu_block_md *block, int start, int end) * the scan_hint if it is larger than or equal and farther than * the current scan_hint. */ - if ((start < block->contig_hint_start && - (contig > block->scan_hint || - (contig == block->scan_hint && - start > block->scan_hint_start)))) { - block->scan_hint_start = start; - block->scan_hint = contig; + if ((free.start < block->contig_hint.start && + (free.size > block->scan_hint.size || + (free.size == block->scan_hint.size && + free.start > block->scan_hint.start)))) { + block->scan_hint = free; } } } @@ -741,8 +737,8 @@ static void pcpu_block_update_scan(struct pcpu_chunk *chunk, int bit_off, * Iterates over the metadata blocks to find the largest contig area. * A full scan can be avoided on the allocation path as this is triggered * if we broke the contig_hint. In doing so, the scan_hint will be before - * the contig_hint or after if the scan_hint == contig_hint. This cannot - * be prevented on freeing as we want to find the largest area possibly + * the contig_hint or after if the scan_hint.size == contig_hint.size. This + * cannot be prevented on freeing as we want to find the largest area possibly * spanning blocks. */ static void pcpu_chunk_refresh_hint(struct pcpu_chunk *chunk, bool full_scan) @@ -751,14 +747,13 @@ static void pcpu_chunk_refresh_hint(struct pcpu_chunk *chunk, bool full_scan) int bit_off, bits; /* promote scan_hint to contig_hint */ - if (!full_scan && chunk_md->scan_hint) { - bit_off = chunk_md->scan_hint_start + chunk_md->scan_hint; - chunk_md->contig_hint_start = chunk_md->scan_hint_start; + if (!full_scan && chunk_md->scan_hint.size) { + bit_off = chunk_md->scan_hint.start + chunk_md->scan_hint.size; chunk_md->contig_hint = chunk_md->scan_hint; - chunk_md->scan_hint = 0; + chunk_md->scan_hint.size = 0; } else { bit_off = chunk_md->first_free; - chunk_md->contig_hint = 0; + chunk_md->contig_hint.size = 0; } bits = 0; @@ -781,14 +776,13 @@ static void pcpu_block_refresh_hint(struct pcpu_chunk *chunk, int index) unsigned int start, end; /* region start, region end */ /* promote scan_hint to contig_hint */ - if (block->scan_hint) { - start = block->scan_hint_start + block->scan_hint; - block->contig_hint_start = block->scan_hint_start; + if (block->scan_hint.size) { + start = block->scan_hint.start + block->scan_hint.size; block->contig_hint = block->scan_hint; - block->scan_hint = 0; + block->scan_hint.size = 0; } else { start = block->first_free; - block->contig_hint = 0; + block->contig_hint.size = 0; } block->right_free = 0; @@ -834,7 +828,7 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off, /* * Update s_block. */ - if (s_block->contig_hint == PCPU_BITMAP_BLOCK_BITS) + if (s_block->contig_hint.size == PCPU_BITMAP_BLOCK_BITS) nr_empty_pages++; /* @@ -848,18 +842,13 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off, PCPU_BITMAP_BLOCK_BITS, s_off + bits); - if (s_block->scan_hint && - pcpu_region_overlap(s_block->scan_hint_start, - s_block->scan_hint_start + s_block->scan_hint, - s_off, - s_off + bits)) - s_block->scan_hint = 0; - - if (pcpu_region_overlap(s_block->contig_hint_start, - s_block->contig_hint_start + - s_block->contig_hint, - s_off, - s_off + bits)) { + struct pcpu_region s_region = { .start = s_off, .size = bits }; + + if (s_block->scan_hint.size && + pcpu_region_overlap(s_block->scan_hint, s_region)) + s_block->scan_hint.size = 0; + + if (pcpu_region_overlap(s_block->contig_hint, s_region)) { /* block contig hint is broken - scan to fix it */ if (!s_off) s_block->left_free = 0; @@ -878,7 +867,7 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off, * Update e_block. */ if (s_index != e_index) { - if (e_block->contig_hint == PCPU_BITMAP_BLOCK_BITS) + if (e_block->contig_hint.size == PCPU_BITMAP_BLOCK_BITS) nr_empty_pages++; /* @@ -893,12 +882,12 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off, /* reset the block */ e_block++; } else { - if (e_block->scan_hint && - e_off > e_block->scan_hint_start) - e_block->scan_hint = 0; + if (e_block->scan_hint.size && + e_off > e_block->scan_hint.start) + e_block->scan_hint.size = 0; e_block->left_free = 0; - if (e_off > e_block->contig_hint_start) { + if (e_off > e_block->contig_hint.start) { /* contig hint is broken - scan to fix it */ pcpu_block_refresh_hint(chunk, e_index); } else { @@ -911,8 +900,8 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off, /* update in-between md_blocks */ nr_empty_pages += (e_index - s_index - 1); for (block = s_block + 1; block < e_block; block++) { - block->scan_hint = 0; - block->contig_hint = 0; + block->scan_hint.size = 0; + block->contig_hint.size = 0; block->left_free = 0; block->right_free = 0; } @@ -927,24 +916,18 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off, if (nr_empty_pages) pcpu_update_empty_pages(chunk, -nr_empty_pages); - if (chunk_md->scan_hint && - pcpu_region_overlap(chunk_md->scan_hint_start, - chunk_md->scan_hint_start + - chunk_md->scan_hint, - bit_off, - bit_off + bits)) - chunk_md->scan_hint = 0; + struct pcpu_region req_region = { .start = bit_off, .size = bits }; + + if (chunk_md->scan_hint.size && + pcpu_region_overlap(chunk_md->scan_hint, req_region)) + chunk_md->scan_hint.size = 0; /* * The only time a full chunk scan is required is if the chunk * 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_md->contig_hint_start, - chunk_md->contig_hint_start + - chunk_md->contig_hint, - bit_off, - bit_off + bits)) + if (pcpu_region_overlap(chunk_md->contig_hint, req_region)) pcpu_chunk_refresh_hint(chunk, false); } @@ -1000,8 +983,8 @@ static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off, * or end of the block. */ start = s_off; - if (s_off == s_block->contig_hint + s_block->contig_hint_start) { - start = s_block->contig_hint_start; + if (s_off == s_block->contig_hint.size + s_block->contig_hint.start) { + start = s_block->contig_hint.start; } else { /* * Scan backwards to find the extent of the free area. @@ -1015,8 +998,8 @@ static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off, } end = e_off; - if (e_off == e_block->contig_hint_start) - end = e_block->contig_hint_start + e_block->contig_hint; + if (e_off == e_block->contig_hint.start) + end = e_block->contig_hint.start + e_block->contig_hint.size; else end = find_next_bit(pcpu_index_alloc_map(chunk, e_index), PCPU_BITMAP_BLOCK_BITS, end); @@ -1038,9 +1021,11 @@ static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off, nr_empty_pages += (e_index - s_index - 1); for (block = s_block + 1; block < e_block; block++) { block->first_free = 0; - block->scan_hint = 0; - block->contig_hint_start = 0; - block->contig_hint = PCPU_BITMAP_BLOCK_BITS; + block->scan_hint.size = 0; + block->contig_hint = (struct pcpu_region){ + .start = 0, + .size = PCPU_BITMAP_BLOCK_BITS, + }; block->left_free = PCPU_BITMAP_BLOCK_BITS; block->right_free = PCPU_BITMAP_BLOCK_BITS; } @@ -1314,8 +1299,9 @@ static int pcpu_free_area(struct pcpu_chunk *chunk, int off) static void pcpu_init_md_block(struct pcpu_block_md *block, int nr_bits) { - block->scan_hint = 0; - block->contig_hint = nr_bits; + block->scan_hint = (struct pcpu_region){ .start = 0, .size = 0 }; + block->contig_hint = + (struct pcpu_region){ .start = 0, .size = nr_bits }; block->left_free = nr_bits; block->right_free = nr_bits; block->first_free = 0; @@ -2141,7 +2127,7 @@ static void pcpu_reclaim_populated(void) * (first) page in the chunk. */ block = chunk->md_blocks + i; - if (block->contig_hint == PCPU_BITMAP_BLOCK_BITS && + if (block->contig_hint.size == PCPU_BITMAP_BLOCK_BITS && test_bit(i, chunk->populated)) { if (end == -1) end = i; -- 2.54.0.563.g4f69b47b94-goog