diff options
| -rw-r--r-- | mm/percpu-internal.h | 9 | ||||
| -rw-r--r-- | mm/percpu.c | 101 |
2 files changed, 103 insertions, 7 deletions
diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h index b1739dc06b73..ec58b244545d 100644 --- a/mm/percpu-internal.h +++ b/mm/percpu-internal.h @@ -9,8 +9,17 @@ * pcpu_block_md is the metadata block struct. * Each chunk's bitmap is split into a number of full blocks. * All units are in terms of bits. + * + * 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. */ 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 */ diff --git a/mm/percpu.c b/mm/percpu.c index 0e98616501b3..48c3da6cff7f 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -320,6 +320,34 @@ static unsigned long pcpu_block_off_to_off(int index, int off) return index * PCPU_BITMAP_BLOCK_BITS + off; } +/* + * pcpu_next_hint - determine which hint to use + * @block: block of interest + * @alloc_bits: size of allocation + * + * 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 + * cannot fulfill an allocation, we can begin scanning from there knowing + * the contig_hint will be our fallback. + */ +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. + */ + 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; + + return block->first_free; +} + /** * pcpu_next_md_free_region - finds the next hint free area * @chunk: chunk of interest @@ -415,9 +443,11 @@ static void pcpu_next_fit_region(struct pcpu_chunk *chunk, int alloc_bits, if (block->contig_hint && block->contig_hint_start >= block_off && block->contig_hint >= *bits + alloc_bits) { + int start = pcpu_next_hint(block, alloc_bits); + *bits += alloc_bits + block->contig_hint_start - - block->first_free; - *bit_off = pcpu_block_off_to_off(i, block->first_free); + start; + *bit_off = pcpu_block_off_to_off(i, start); return; } /* reset to satisfy the second predicate above */ @@ -628,12 +658,57 @@ static void pcpu_block_update(struct pcpu_block_md *block, int start, int end) block->right_free = contig; if (contig > block->contig_hint) { + /* promote the old contig_hint to be the new scan_hint */ + if (start > block->contig_hint_start) { + if (block->contig_hint > block->scan_hint) { + block->scan_hint_start = + block->contig_hint_start; + block->scan_hint = block->contig_hint; + } else if (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. + */ + block->scan_hint = 0; + } + } else { + block->scan_hint = 0; + } 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; + } 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 (start < block->scan_hint_start && + block->contig_hint > block->scan_hint) + block->scan_hint = 0; + } else if (start > block->scan_hint_start || + block->contig_hint > block->scan_hint) { + /* + * Knowing contig == contig_hint, 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; + } + } else { + /* + * The region is smaller than the contig_hint. So only update + * 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; + } } } @@ -652,7 +727,7 @@ static void pcpu_block_refresh_hint(struct pcpu_chunk *chunk, int index) int rs, re; /* region start, region end */ /* clear hints */ - block->contig_hint = 0; + block->contig_hint = block->scan_hint = 0; block->left_free = block->right_free = 0; /* iterate over free areas and update the contig hints */ @@ -709,6 +784,12 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off, PCPU_BITMAP_BLOCK_BITS, s_off + bits); + if (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, @@ -745,6 +826,9 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off, /* reset the block */ e_block++; } else { + if (e_off > e_block->scan_hint_start) + e_block->scan_hint = 0; + if (e_off > e_block->contig_hint_start) { /* contig hint is broken - scan to fix it */ pcpu_block_refresh_hint(chunk, e_index); @@ -759,6 +843,7 @@ 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->left_free = 0; block->right_free = 0; @@ -869,6 +954,7 @@ 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->left_free = PCPU_BITMAP_BLOCK_BITS; @@ -1080,6 +1166,7 @@ static void pcpu_init_md_blocks(struct pcpu_chunk *chunk) for (md_block = chunk->md_blocks; md_block != chunk->md_blocks + pcpu_chunk_nr_blocks(chunk); md_block++) { + md_block->scan_hint = 0; md_block->contig_hint = PCPU_BITMAP_BLOCK_BITS; md_block->left_free = PCPU_BITMAP_BLOCK_BITS; md_block->right_free = PCPU_BITMAP_BLOCK_BITS; |