From d2f3c3849461baefdbb39123abde1054d46bf22e Mon Sep 17 00:00:00 2001 From: "Dennis Zhou (Facebook)" Date: Mon, 24 Jul 2017 19:02:09 -0400 Subject: percpu: increase minimum percpu allocation size and align first regions This patch increases the minimum allocation size of percpu memory to 4-bytes. This change will help minimize the metadata overhead associated with the bitmap allocator. The assumption is that most allocations will be of objects or structs greater than 2 bytes with integers or longs being used rather than shorts. The first chunk regions are now aligned with the minimum allocation size. The reserved region is expected to be set as a multiple of the minimum allocation size. The static region is aligned up and the delta is removed from the dynamic size. This works because the dynamic size is increased to be page aligned. If the static size is not minimum allocation size aligned, then there must be a gap that is added to the dynamic size. The dynamic size will never be smaller than the set value. Signed-off-by: Dennis Zhou Reviewed-by: Josef Bacik Signed-off-by: Tejun Heo --- mm/percpu.c | 27 ++++++++++++++++++++------- 1 file changed, 20 insertions(+), 7 deletions(-) (limited to 'mm') diff --git a/mm/percpu.c b/mm/percpu.c index 657ab0821cf0..dc755721c333 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -956,10 +956,10 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved, * We want the lowest bit of offset available for in-use/free * indicator, so force >= 16bit alignment and make size even. */ - if (unlikely(align < 2)) - align = 2; + if (unlikely(align < PCPU_MIN_ALLOC_SIZE)) + align = PCPU_MIN_ALLOC_SIZE; - size = ALIGN(size, 2); + size = ALIGN(size, PCPU_MIN_ALLOC_SIZE); if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE || !is_power_of_2(align))) { @@ -1653,6 +1653,7 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai, static int smap[PERCPU_DYNAMIC_EARLY_SLOTS] __initdata; static int dmap[PERCPU_DYNAMIC_EARLY_SLOTS] __initdata; size_t size_sum = ai->static_size + ai->reserved_size + ai->dyn_size; + size_t static_size, dyn_size; struct pcpu_chunk *chunk; unsigned long *group_offsets; size_t *group_sizes; @@ -1686,6 +1687,7 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai, PCPU_SETUP_BUG_ON(ai->unit_size < PCPU_MIN_UNIT_SIZE); PCPU_SETUP_BUG_ON(ai->dyn_size < PERCPU_DYNAMIC_EARLY_SIZE); PCPU_SETUP_BUG_ON(!ai->dyn_size); + PCPU_SETUP_BUG_ON(!IS_ALIGNED(ai->reserved_size, PCPU_MIN_ALLOC_SIZE)); PCPU_SETUP_BUG_ON(pcpu_verify_alloc_info(ai) < 0); /* process group information and build config tables accordingly */ @@ -1763,6 +1765,17 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai, for (i = 0; i < pcpu_nr_slots; i++) INIT_LIST_HEAD(&pcpu_slot[i]); + /* + * The end of the static region needs to be aligned with the + * minimum allocation size as this offsets the reserved and + * dynamic region. The first chunk ends page aligned by + * expanding the dynamic region, therefore the dynamic region + * can be shrunk to compensate while still staying above the + * configured sizes. + */ + static_size = ALIGN(ai->static_size, PCPU_MIN_ALLOC_SIZE); + dyn_size = ai->dyn_size - (static_size - ai->static_size); + /* * Initialize first chunk. * If the reserved_size is non-zero, this initializes the reserved @@ -1771,8 +1784,8 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai, * pcpu_first_chunk, will always point to the chunk that serves * the dynamic region. */ - tmp_addr = (unsigned long)base_addr + ai->static_size; - map_size = ai->reserved_size ?: ai->dyn_size; + tmp_addr = (unsigned long)base_addr + static_size; + map_size = ai->reserved_size ?: dyn_size; chunk = pcpu_alloc_first_chunk(tmp_addr, map_size, smap, ARRAY_SIZE(smap)); @@ -1780,9 +1793,9 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai, if (ai->reserved_size) { pcpu_reserved_chunk = chunk; - tmp_addr = (unsigned long)base_addr + ai->static_size + + tmp_addr = (unsigned long)base_addr + static_size + ai->reserved_size; - map_size = ai->dyn_size; + map_size = dyn_size; chunk = pcpu_alloc_first_chunk(tmp_addr, map_size, dmap, ARRAY_SIZE(dmap)); } -- cgit v1.2.1