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Date: Fri, 22 Aug 2014 12:53:17 -0400
From: Tejun Heo <tj@...nel.org>
To: akpm@...ux-foundation.org, cl@...ux-foundation.org
Cc: laijs@...fujitsu.com, linux-kernel@...r.kernel.org,
vgoyal@...hat.com, Tejun Heo <tj@...nel.org>
Subject: [PATCH 13/15] percpu: implmeent pcpu_nr_empty_pop_pages and chunk->nr_populated
pcpu_nr_empty_pop_pages counts the number of empty populated pages
across all chunks and chunk->nr_populated counts the number of
populated pages in a chunk. Both will be used to implement pre/async
population for atomic allocations.
pcpu_chunk_[de]populated() are added to update chunk->populated,
chunk->nr_populated and pcpu_nr_empty_pop_pages together. All
successful chunk [de]populations should be followed by the
corresponding pcpu_chunk_[de]populated() calls.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
mm/percpu-km.c | 2 +-
mm/percpu.c | 122 ++++++++++++++++++++++++++++++++++++++++++++++++++++-----
2 files changed, 114 insertions(+), 10 deletions(-)
diff --git a/mm/percpu-km.c b/mm/percpu-km.c
index e662b49..10e3d0b 100644
--- a/mm/percpu-km.c
+++ b/mm/percpu-km.c
@@ -69,7 +69,7 @@ static struct pcpu_chunk *pcpu_create_chunk(void)
chunk->base_addr = page_address(pages) - pcpu_group_offsets[0];
spin_lock_irq(&pcpu_lock);
- bitmap_fill(chunk->populated, nr_pages);
+ pcpu_chunk_populated(chunk, 0, nr_pages);
spin_unlock_irq(&pcpu_lock);
return chunk;
diff --git a/mm/percpu.c b/mm/percpu.c
index d6b36e7..7f076ed 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -113,6 +113,7 @@ struct pcpu_chunk {
void *data; /* chunk data */
int first_free; /* no free below this */
bool immutable; /* no [de]population allowed */
+ int nr_populated; /* # of populated pages */
unsigned long populated[]; /* populated bitmap */
};
@@ -161,6 +162,12 @@ static DEFINE_MUTEX(pcpu_alloc_mutex); /* chunk create/destroy, [de]pop */
static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */
+/*
+ * The number of empty populated pages, protected by pcpu_lock. The
+ * reserved chunk doesn't contribute to the count.
+ */
+static int pcpu_nr_empty_pop_pages;
+
/* reclaim work to release fully free chunks, scheduled from free path */
static void pcpu_reclaim(struct work_struct *work);
static DECLARE_WORK(pcpu_reclaim_work, pcpu_reclaim);
@@ -296,6 +303,38 @@ static void pcpu_mem_free(void *ptr, size_t size)
}
/**
+ * pcpu_count_occupied_pages - count the number of pages an area occupies
+ * @chunk: chunk of interest
+ * @i: index of the area in question
+ *
+ * Count the number of pages chunk's @i'th area occupies. When the area's
+ * start and/or end address isn't aligned to page boundary, the straddled
+ * page is included in the count iff the rest of the page is free.
+ */
+static int pcpu_count_occupied_pages(struct pcpu_chunk *chunk, int i)
+{
+ int off = chunk->map[i] & ~1;
+ int end = chunk->map[i + 1] & ~1;
+
+ if (!PAGE_ALIGNED(off) && i > 0) {
+ int prev = chunk->map[i - 1];
+
+ if (!(prev & 1) && prev <= round_down(off, PAGE_SIZE))
+ off = round_down(off, PAGE_SIZE);
+ }
+
+ if (!PAGE_ALIGNED(end) && i + 1 < chunk->map_used) {
+ int next = chunk->map[i + 1];
+ int nend = chunk->map[i + 2] & ~1;
+
+ if (!(next & 1) && nend >= round_up(end, PAGE_SIZE))
+ end = round_up(end, PAGE_SIZE);
+ }
+
+ return max_t(int, PFN_DOWN(end) - PFN_UP(off), 0);
+}
+
+/**
* pcpu_chunk_relocate - put chunk in the appropriate chunk slot
* @chunk: chunk of interest
* @oslot: the previous slot it was on
@@ -483,6 +522,7 @@ static int pcpu_fit_in_area(struct pcpu_chunk *chunk, int off, int this_size,
* @size: wanted size in bytes
* @align: wanted align
* @pop_only: allocate only from the populated area
+ * @occ_pages_p: out param for the number of pages the area occupies
*
* Try to allocate @size bytes area aligned at @align from @chunk.
* Note that this function only allocates the offset. It doesn't
@@ -498,7 +538,7 @@ static int pcpu_fit_in_area(struct pcpu_chunk *chunk, int off, int this_size,
* found.
*/
static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align,
- bool pop_only)
+ bool pop_only, int *occ_pages_p)
{
int oslot = pcpu_chunk_slot(chunk);
int max_contig = 0;
@@ -587,6 +627,7 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align,
chunk->free_size -= size;
*p |= 1;
+ *occ_pages_p = pcpu_count_occupied_pages(chunk, i);
pcpu_chunk_relocate(chunk, oslot);
return off;
}
@@ -602,6 +643,7 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align,
* pcpu_free_area - free area to a pcpu_chunk
* @chunk: chunk of interest
* @freeme: offset of area to free
+ * @occ_pages_p: out param for the number of pages the area occupies
*
* Free area starting from @freeme to @chunk. Note that this function
* only modifies the allocation map. It doesn't depopulate or unmap
@@ -610,7 +652,8 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align,
* CONTEXT:
* pcpu_lock.
*/
-static void pcpu_free_area(struct pcpu_chunk *chunk, int freeme)
+static void pcpu_free_area(struct pcpu_chunk *chunk, int freeme,
+ int *occ_pages_p)
{
int oslot = pcpu_chunk_slot(chunk);
int off = 0;
@@ -641,6 +684,8 @@ static void pcpu_free_area(struct pcpu_chunk *chunk, int freeme)
*p = off &= ~1;
chunk->free_size += (p[1] & ~1) - off;
+ *occ_pages_p = pcpu_count_occupied_pages(chunk, i);
+
/* merge with next? */
if (!(p[1] & 1))
to_free++;
@@ -696,6 +741,50 @@ static void pcpu_free_chunk(struct pcpu_chunk *chunk)
pcpu_mem_free(chunk, pcpu_chunk_struct_size);
}
+/**
+ * pcpu_chunk_populated - post-population bookkeeping
+ * @chunk: pcpu_chunk which got populated
+ * @page_start: the start page
+ * @page_end: the end page
+ *
+ * Pages in [@page_start,@page_end) have been populated to @chunk. Update
+ * the bookkeeping information accordingly. Must be called after each
+ * successful population.
+ */
+static void pcpu_chunk_populated(struct pcpu_chunk *chunk,
+ int page_start, int page_end)
+{
+ int nr = page_end - page_start;
+
+ lockdep_assert_held(&pcpu_lock);
+
+ bitmap_set(chunk->populated, page_start, nr);
+ chunk->nr_populated += nr;
+ pcpu_nr_empty_pop_pages += nr;
+}
+
+/**
+ * pcpu_chunk_depopulated - post-depopulation bookkeeping
+ * @chunk: pcpu_chunk which got depopulated
+ * @page_start: the start page
+ * @page_end: the end page
+ *
+ * Pages in [@page_start,@page_end) have been depopulated from @chunk.
+ * Update the bookkeeping information accordingly. Must be called after
+ * each successful depopulation.
+ */
+static void pcpu_chunk_depopulated(struct pcpu_chunk *chunk,
+ int page_start, int page_end)
+{
+ int nr = page_end - page_start;
+
+ lockdep_assert_held(&pcpu_lock);
+
+ bitmap_clear(chunk->populated, page_start, nr);
+ chunk->nr_populated -= nr;
+ pcpu_nr_empty_pop_pages -= nr;
+}
+
/*
* Chunk management implementation.
*
@@ -772,6 +861,7 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
struct pcpu_chunk *chunk;
const char *err;
bool is_atomic = !(gfp & GFP_KERNEL);
+ int occ_pages = 0;
int slot, off, new_alloc, cpu, ret;
unsigned long flags;
void __percpu *ptr;
@@ -812,7 +902,8 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
spin_lock_irqsave(&pcpu_lock, flags);
}
- off = pcpu_alloc_area(chunk, size, align, is_atomic);
+ off = pcpu_alloc_area(chunk, size, align, is_atomic,
+ &occ_pages);
if (off >= 0)
goto area_found;
@@ -845,7 +936,8 @@ restart:
goto restart;
}
- off = pcpu_alloc_area(chunk, size, align, is_atomic);
+ off = pcpu_alloc_area(chunk, size, align, is_atomic,
+ &occ_pages);
if (off >= 0)
goto area_found;
}
@@ -899,17 +991,20 @@ area_found:
spin_lock_irqsave(&pcpu_lock, flags);
if (ret) {
mutex_unlock(&pcpu_alloc_mutex);
- pcpu_free_area(chunk, off);
+ pcpu_free_area(chunk, off, &occ_pages);
err = "failed to populate";
goto fail_unlock;
}
- bitmap_set(chunk->populated, rs, re - rs);
+ pcpu_chunk_populated(chunk, rs, re);
spin_unlock_irqrestore(&pcpu_lock, flags);
}
mutex_unlock(&pcpu_alloc_mutex);
}
+ if (chunk != pcpu_reserved_chunk)
+ pcpu_nr_empty_pop_pages -= occ_pages;
+
/* clear the areas and return address relative to base address */
for_each_possible_cpu(cpu)
memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
@@ -1019,7 +1114,9 @@ static void pcpu_reclaim(struct work_struct *work)
pcpu_for_each_pop_region(chunk, rs, re, 0, pcpu_unit_pages) {
pcpu_depopulate_chunk(chunk, rs, re);
- bitmap_clear(chunk->populated, rs, re - rs);
+ spin_lock_irq(&pcpu_lock);
+ pcpu_chunk_depopulated(chunk, rs, re);
+ spin_unlock_irq(&pcpu_lock);
}
pcpu_destroy_chunk(chunk);
}
@@ -1041,7 +1138,7 @@ void free_percpu(void __percpu *ptr)
void *addr;
struct pcpu_chunk *chunk;
unsigned long flags;
- int off;
+ int off, occ_pages;
if (!ptr)
return;
@@ -1055,7 +1152,10 @@ void free_percpu(void __percpu *ptr)
chunk = pcpu_chunk_addr_search(addr);
off = addr - chunk->base_addr;
- pcpu_free_area(chunk, off);
+ pcpu_free_area(chunk, off, &occ_pages);
+
+ if (chunk != pcpu_reserved_chunk)
+ pcpu_nr_empty_pop_pages += occ_pages;
/* if there are more than one fully free chunks, wake up grim reaper */
if (chunk->free_size == pcpu_unit_size) {
@@ -1459,6 +1559,7 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
schunk->map_alloc = ARRAY_SIZE(smap);
schunk->immutable = true;
bitmap_fill(schunk->populated, pcpu_unit_pages);
+ schunk->nr_populated = pcpu_unit_pages;
if (ai->reserved_size) {
schunk->free_size = ai->reserved_size;
@@ -1488,6 +1589,7 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
dchunk->map_alloc = ARRAY_SIZE(dmap);
dchunk->immutable = true;
bitmap_fill(dchunk->populated, pcpu_unit_pages);
+ dchunk->nr_populated = pcpu_unit_pages;
dchunk->contig_hint = dchunk->free_size = dyn_size;
dchunk->map[0] = 1;
@@ -1498,6 +1600,8 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
/* link the first chunk in */
pcpu_first_chunk = dchunk ?: schunk;
+ pcpu_nr_empty_pop_pages +=
+ pcpu_count_occupied_pages(pcpu_first_chunk, 1);
pcpu_chunk_relocate(pcpu_first_chunk, -1);
/* we're done */
--
1.9.3
--
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