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percpu: speed alloc_pcpu_area() up

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If we know that first N areas are all in use, we can obviously skip
them when searching for a free one.  And that kind of hint is very
easy to maintain.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Al Viro 2014-03-06 20:52:32 -05:00 committed by Tejun Heo
parent 723ad1d90b
commit 3d331ad74f
1 changed files with 17 additions and 1 deletions
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18
mm/percpu.c
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@ -106,6 +106,7 @@ struct pcpu_chunk {
int map_alloc; /* # of map entries allocated */ int map_alloc; /* # of map entries allocated */
int *map; /* allocation map */ int *map; /* allocation map */
void *data; /* chunk data */ void *data; /* chunk data */
int first_free; /* no free below this */
bool immutable; /* no [de]population allowed */ bool immutable; /* no [de]population allowed */
unsigned long populated[]; /* populated bitmap */ unsigned long populated[]; /* populated bitmap */
}; };
@ -441,9 +442,10 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
int oslot = pcpu_chunk_slot(chunk); int oslot = pcpu_chunk_slot(chunk);
int max_contig = 0; int max_contig = 0;
int i, off; int i, off;
bool seen_free = false;
int *p; int *p;
for (i = 0, p = chunk->map; i < chunk->map_used; i++, p++) { for (i = chunk->first_free, p = chunk->map + i; i < chunk->map_used; i++, p++) {
int head, tail; int head, tail;
int this_size; int this_size;
@ -456,6 +458,10 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
this_size = (p[1] & ~1) - off; this_size = (p[1] & ~1) - off;
if (this_size < head + size) { if (this_size < head + size) {
if (!seen_free) {
chunk->first_free = i;
seen_free = true;
}
max_contig = max(this_size, max_contig); max_contig = max(this_size, max_contig);
continue; continue;
} }
@ -491,6 +497,10 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
chunk->map_used += nr_extra; chunk->map_used += nr_extra;
if (head) { if (head) {
if (!seen_free) {
chunk->first_free = i;
seen_free = true;
}
*++p = off += head; *++p = off += head;
++i; ++i;
max_contig = max(head, max_contig); max_contig = max(head, max_contig);
@ -501,6 +511,9 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
} }
} }
if (!seen_free)
chunk->first_free = i + 1;
/* update hint and mark allocated */ /* update hint and mark allocated */
if (i + 1 == chunk->map_used) if (i + 1 == chunk->map_used)
chunk->contig_hint = max_contig; /* fully scanned */ chunk->contig_hint = max_contig; /* fully scanned */
@ -558,6 +571,9 @@ static void pcpu_free_area(struct pcpu_chunk *chunk, int freeme)
} }
BUG_ON(off != freeme); BUG_ON(off != freeme);
if (i < chunk->first_free)
chunk->first_free = i;
p = chunk->map + i; p = chunk->map + i;
*p = off &= ~1; *p = off &= ~1;
chunk->free_size += (p[1] & ~1) - off; chunk->free_size += (p[1] & ~1) - off;