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Commit 3d331ad7 authored by Al Viro's avatar Al Viro Committed by Tejun Heo
Browse files

percpu: speed alloc_pcpu_area() up 



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: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 723ad1d9

mm/percpu.c

+17 −1
Original line number Diff line number Diff line
@@ -106,6 +106,7 @@ struct pcpu_chunk { 
	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 */

};
@@ -441,9 +442,10 @@ 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;

	bool seen_free = false;

	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 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;

		if (this_size < head + size) {

			if (!seen_free) {

				chunk->first_free = i;

				seen_free = true;

			}

			max_contig = max(this_size, max_contig);

			continue;

		}
@@ -491,6 +497,10 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align) 
			chunk->map_used += nr_extra;



			if (head) {

				if (!seen_free) {

					chunk->first_free = i;

					seen_free = true;

				}

				*++p = off += head;

				++i;

				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 */

		if (i + 1 == chunk->map_used)

			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);



	if (i < chunk->first_free)

		chunk->first_free = i;



	p = chunk->map + i;

	*p = off &= ~1;

	chunk->free_size += (p[1] & ~1) - off;