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Date: Wed, 5 Mar 2014 03:49:19 +0000
From: Al Viro <viro@...IV.linux.org.uk>
To: linux-fsdevel@...r.kernel.org
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
linux-kernel@...r.kernel.org, Stephen Tweedie <sct@...hat.com>,
Jeremy Eder <jeder@...hat.com>
Subject: [PATCH 1/5][RFC][CFT] percpu fixes, part 1
convert ->map[] to array of offsets, cache the "no free areas among the
first N" in chunk. Free/in-use is represented by the LSB, a sentry
element (<free = false, offset = total size of chunk>) is added in
the end.
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
mm/percpu.c | 165 +++++++++++++++++++++++++++++++++++++----------------------
1 file changed, 103 insertions(+), 62 deletions(-)
diff --git a/mm/percpu.c b/mm/percpu.c
index 036cfe0..4469fbd 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -102,10 +102,11 @@ struct pcpu_chunk {
int free_size; /* free bytes in the chunk */
int contig_hint; /* max contiguous size hint */
void *base_addr; /* base address of this chunk */
- int map_used; /* # of map entries used */
+ int map_used; /* # of map entries used before the sentry */
int map_alloc; /* # of map entries allocated */
int *map; /* allocation map */
void *data; /* chunk data */
+ int first_free; /* no free below this */
bool immutable; /* no [de]population allowed */
unsigned long populated[]; /* populated bitmap */
};
@@ -356,11 +357,11 @@ static int pcpu_need_to_extend(struct pcpu_chunk *chunk)
{
int new_alloc;
- if (chunk->map_alloc >= chunk->map_used + 2)
+ if (chunk->map_alloc >= chunk->map_used + 3)
return 0;
new_alloc = PCPU_DFL_MAP_ALLOC;
- while (new_alloc < chunk->map_used + 2)
+ while (new_alloc < chunk->map_used + 3)
new_alloc *= 2;
return new_alloc;
@@ -438,25 +439,24 @@ out_unlock:
* pcpu_lock.
*/
static void pcpu_split_block(struct pcpu_chunk *chunk, int i,
- int head, int tail)
+ int head, int size, int tail)
{
int nr_extra = !!head + !!tail;
+ int off;
- BUG_ON(chunk->map_alloc < chunk->map_used + nr_extra);
+ BUG_ON(chunk->map_alloc <= chunk->map_used + nr_extra);
/* insert new subblocks */
- memmove(&chunk->map[i + nr_extra], &chunk->map[i],
+ memmove(&chunk->map[i + nr_extra] + 1, &chunk->map[i] + 1,
sizeof(chunk->map[0]) * (chunk->map_used - i));
chunk->map_used += nr_extra;
- if (head) {
- chunk->map[i + 1] = chunk->map[i] - head;
- chunk->map[i++] = head;
- }
- if (tail) {
- chunk->map[i++] -= tail;
- chunk->map[i] = tail;
- }
+ off = chunk->map[i];
+
+ if (head)
+ chunk->map[++i] = off += head;
+ if (tail)
+ chunk->map[++i] = off += size;
}
/**
@@ -483,19 +483,27 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
int oslot = pcpu_chunk_slot(chunk);
int max_contig = 0;
int i, off;
+ int seen_free = 0;
+ int *p;
- for (i = 0, off = 0; i < chunk->map_used; off += abs(chunk->map[i++])) {
- bool is_last = i + 1 == chunk->map_used;
+ for (i = chunk->first_free, p = chunk->map + i; i < chunk->map_used; i++, p++) {
int head, tail;
+ int this_size;
+
+ off = *p;
+ if (off & 1)
+ continue;
/* extra for alignment requirement */
head = ALIGN(off, align) - off;
- BUG_ON(i == 0 && head != 0);
- if (chunk->map[i] < 0)
- continue;
- if (chunk->map[i] < head + size) {
- max_contig = max(chunk->map[i], max_contig);
+ this_size = (p[1] & ~1) - off;
+ if (this_size < head + size) {
+ if (!seen_free) {
+ chunk->first_free = i;
+ seen_free = 1;
+ }
+ max_contig = max(this_size, max_contig);
continue;
}
@@ -505,44 +513,50 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
* than sizeof(int), which is very small but isn't too
* uncommon for percpu allocations.
*/
- if (head && (head < sizeof(int) || chunk->map[i - 1] > 0)) {
- if (chunk->map[i - 1] > 0)
- chunk->map[i - 1] += head;
- else {
- chunk->map[i - 1] -= head;
+ if (head && (head < sizeof(int) || !(p[-1] & 1))) {
+ if (p[-1] & 1)
chunk->free_size -= head;
- }
- chunk->map[i] -= head;
- off += head;
+ *p = off += head;
+ this_size -= head;
head = 0;
}
/* if tail is small, just keep it around */
- tail = chunk->map[i] - head - size;
- if (tail < sizeof(int))
+ tail = this_size - head - size;
+ if (tail < sizeof(int)) {
tail = 0;
+ size = this_size - head;
+ }
/* split if warranted */
if (head || tail) {
- pcpu_split_block(chunk, i, head, tail);
+ pcpu_split_block(chunk, i, head, size, tail);
if (head) {
+ if (!seen_free) {
+ chunk->first_free = i;
+ seen_free = 1;
+ }
i++;
+ p++;
off += head;
- max_contig = max(chunk->map[i - 1], max_contig);
+ max_contig = max(head, max_contig);
}
if (tail)
- max_contig = max(chunk->map[i + 1], max_contig);
+ max_contig = max(tail, max_contig);
}
+ if (!seen_free)
+ chunk->first_free = i + 1;
+
/* update hint and mark allocated */
- if (is_last)
+ if (i + 1 == chunk->map_used)
chunk->contig_hint = max_contig; /* fully scanned */
else
chunk->contig_hint = max(chunk->contig_hint,
max_contig);
- chunk->free_size -= chunk->map[i];
- chunk->map[i] = -chunk->map[i];
+ chunk->free_size -= size;
+ *p |= 1;
pcpu_chunk_relocate(chunk, oslot);
return off;
@@ -570,34 +584,50 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
static void pcpu_free_area(struct pcpu_chunk *chunk, int freeme)
{
int oslot = pcpu_chunk_slot(chunk);
- int i, off;
-
- for (i = 0, off = 0; i < chunk->map_used; off += abs(chunk->map[i++]))
- if (off == freeme)
- break;
+ int off = 0;
+ unsigned i, j;
+ int to_free = 0;
+ int *p;
+
+ freeme |= 1;
+
+ i = 0;
+ j = chunk->map_used;
+ while (i != j) {
+ unsigned k = (i + j) / 2;
+ off = chunk->map[k];
+ if (off < freeme)
+ i = k + 1;
+ else if (off > freeme)
+ j = k;
+ else
+ i = j = k;
+ }
BUG_ON(off != freeme);
- BUG_ON(chunk->map[i] > 0);
- chunk->map[i] = -chunk->map[i];
- chunk->free_size += chunk->map[i];
+ if (i < chunk->first_free)
+ chunk->first_free = i;
+
+ p = chunk->map + i;
+ *p = off &= ~1;
+ chunk->free_size += (p[1] & ~1) - off;
+ /* merge with next? */
+ if (!(p[1] & 1))
+ to_free++;
/* merge with previous? */
- if (i > 0 && chunk->map[i - 1] >= 0) {
- chunk->map[i - 1] += chunk->map[i];
- chunk->map_used--;
- memmove(&chunk->map[i], &chunk->map[i + 1],
- (chunk->map_used - i) * sizeof(chunk->map[0]));
+ if (i > 0 && !(p[-1] & 1)) {
+ to_free++;
i--;
+ p--;
}
- /* merge with next? */
- if (i + 1 < chunk->map_used && chunk->map[i + 1] >= 0) {
- chunk->map[i] += chunk->map[i + 1];
- chunk->map_used--;
- memmove(&chunk->map[i + 1], &chunk->map[i + 2],
- (chunk->map_used - (i + 1)) * sizeof(chunk->map[0]));
+ if (to_free) {
+ chunk->map_used -= to_free;
+ memmove(p + 1, p + 1 + to_free,
+ (chunk->map_used - i) * sizeof(chunk->map[0]));
}
- chunk->contig_hint = max(chunk->map[i], chunk->contig_hint);
+ chunk->contig_hint = max(chunk->map[i + 1] - chunk->map[i] - 1, chunk->contig_hint);
pcpu_chunk_relocate(chunk, oslot);
}
@@ -617,7 +647,9 @@ static struct pcpu_chunk *pcpu_alloc_chunk(void)
}
chunk->map_alloc = PCPU_DFL_MAP_ALLOC;
- chunk->map[chunk->map_used++] = pcpu_unit_size;
+ chunk->map[0] = 0;
+ chunk->map[1] = pcpu_unit_size | 1;
+ chunk->map_used = 1;
INIT_LIST_HEAD(&chunk->list);
chunk->free_size = pcpu_unit_size;
@@ -713,6 +745,9 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved)
unsigned long flags;
void __percpu *ptr;
+ if (unlikely(align < 2))
+ align = 2;
+
if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE)) {
WARN(true, "illegal size (%zu) or align (%zu) for "
"percpu allocation\n", size, align);
@@ -1343,9 +1378,13 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
}
schunk->contig_hint = schunk->free_size;
- schunk->map[schunk->map_used++] = -ai->static_size;
+ schunk->map[0] = 1;
+ schunk->map[1] = ai->static_size;
+ schunk->map_used = 1;
if (schunk->free_size)
- schunk->map[schunk->map_used++] = schunk->free_size;
+ schunk->map[++schunk->map_used] = 1 | (ai->static_size + schunk->free_size);
+ else
+ schunk->map[1] |= 1;
/* init dynamic chunk if necessary */
if (dyn_size) {
@@ -1358,8 +1397,10 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
bitmap_fill(dchunk->populated, pcpu_unit_pages);
dchunk->contig_hint = dchunk->free_size = dyn_size;
- dchunk->map[dchunk->map_used++] = -pcpu_reserved_chunk_limit;
- dchunk->map[dchunk->map_used++] = dchunk->free_size;
+ dchunk->map[0] = 1;
+ dchunk->map[1] = pcpu_reserved_chunk_limit;
+ dchunk->map[2] = (pcpu_reserved_chunk_limit + dchunk->free_size) | 1;
+ dchunk->map_used = 2;
}
/* link the first chunk in */
--
1.7.10.4
--
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