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Commit 5972511b authored by Jens Axboe's avatar Jens Axboe Committed by Jens Axboe
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[BLOCK] Don't pin lots of memory in mempools 



Currently we scale the mempool sizes depending on memory installed
in the machine, except for the bio pool itself which sits at a fixed
256 entry pre-allocation.

There's really no point in "optimizing" this OOM path, we just need
enough preallocated to make progress. A single unit is enough, lets
scale it down to 2 just to be on the safe side.

This patch saves ~150kb of pinned kernel memory on a 32-bit box.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent b9099ff6

drivers/md/dm-crypt.c

+1 −1
Original line number Diff line number Diff line
@@ -867,7 +867,7 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv) 
		goto bad4;

	}



	cc->bs = bioset_create(MIN_IOS, MIN_IOS, 4);

	cc->bs = bioset_create(MIN_IOS, MIN_IOS);

	if (!cc->bs) {

		ti->error = "Cannot allocate crypt bioset";

		goto bad_bs;

drivers/md/dm-io.c

+1 −1
Original line number Diff line number Diff line
@@ -60,7 +60,7 @@ static int resize_pool(unsigned int new_ios) 
		if (!_io_pool)

			return -ENOMEM;



		_bios = bioset_create(16, 16, 4);

		_bios = bioset_create(16, 16);

		if (!_bios) {

			mempool_destroy(_io_pool);

			_io_pool = NULL;

drivers/md/dm.c

+1 −1
Original line number Diff line number Diff line
@@ -1012,7 +1012,7 @@ static struct mapped_device *alloc_dev(int minor) 
	if (!md->tio_pool)

		goto bad3;



	md->bs = bioset_create(16, 16, 4);

	md->bs = bioset_create(16, 16);

	if (!md->bs)

		goto bad_no_bioset;

drivers/scsi/scsi_lib.c

+1 −1
Original line number Diff line number Diff line
@@ -31,7 +31,7 @@ 




#define SG_MEMPOOL_NR		ARRAY_SIZE(scsi_sg_pools)

#define SG_MEMPOOL_SIZE		32

#define SG_MEMPOOL_SIZE		2



struct scsi_host_sg_pool {

	size_t		size;

fs/bio.c

+6 −35
Original line number Diff line number Diff line
@@ -28,7 +28,7 @@ 
#include <linux/blktrace_api.h>

#include <scsi/sg.h>		/* for struct sg_iovec */



#define BIO_POOL_SIZE 256

#define BIO_POOL_SIZE 2



static struct kmem_cache *bio_slab __read_mostly;
@@ -38,7 +38,7 @@ static struct kmem_cache *bio_slab __read_mostly; 
 * a small number of entries is fine, not going to be performance critical.

 * basically we just need to survive

 */

#define BIO_SPLIT_ENTRIES 8	

#define BIO_SPLIT_ENTRIES 2

mempool_t *bio_split_pool __read_mostly;



struct biovec_slab {
@@ -1120,7 +1120,7 @@ struct bio_pair *bio_split(struct bio *bi, mempool_t *pool, int first_sectors) 
 * create memory pools for biovec's in a bio_set.

 * use the global biovec slabs created for general use.

 */

static int biovec_create_pools(struct bio_set *bs, int pool_entries, int scale)

static int biovec_create_pools(struct bio_set *bs, int pool_entries)

{

	int i;
@@ -1128,9 +1128,6 @@ static int biovec_create_pools(struct bio_set *bs, int pool_entries, int scale) 
		struct biovec_slab *bp = bvec_slabs + i;

		mempool_t **bvp = bs->bvec_pools + i;



		if (pool_entries > 1 && i >= scale)

			pool_entries >>= 1;



		*bvp = mempool_create_slab_pool(pool_entries, bp->slab);

		if (!*bvp)

			return -ENOMEM;
@@ -1161,7 +1158,7 @@ void bioset_free(struct bio_set *bs) 
	kfree(bs);

}



struct bio_set *bioset_create(int bio_pool_size, int bvec_pool_size, int scale)

struct bio_set *bioset_create(int bio_pool_size, int bvec_pool_size)

{

	struct bio_set *bs = kzalloc(sizeof(*bs), GFP_KERNEL);
@@ -1172,7 +1169,7 @@ struct bio_set *bioset_create(int bio_pool_size, int bvec_pool_size, int scale) 
	if (!bs->bio_pool)

		goto bad;



	if (!biovec_create_pools(bs, bvec_pool_size, scale))

	if (!biovec_create_pools(bs, bvec_pool_size))

		return bs;



bad:
@@ -1196,38 +1193,12 @@ static void __init biovec_init_slabs(void) 


static int __init init_bio(void)

{

	int megabytes, bvec_pool_entries;

	int scale = BIOVEC_NR_POOLS;



	bio_slab = kmem_cache_create("bio", sizeof(struct bio), 0,

				SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);



	biovec_init_slabs();



	megabytes = nr_free_pages() >> (20 - PAGE_SHIFT);



	/*

	 * find out where to start scaling

	 */

	if (megabytes <= 16)

		scale = 0;

	else if (megabytes <= 32)

		scale = 1;

	else if (megabytes <= 64)

		scale = 2;

	else if (megabytes <= 96)

		scale = 3;

	else if (megabytes <= 128)

		scale = 4;



	/*

	 * Limit number of entries reserved -- mempools are only used when

	 * the system is completely unable to allocate memory, so we only

	 * need enough to make progress.

	 */

	bvec_pool_entries = 1 + scale;



	fs_bio_set = bioset_create(BIO_POOL_SIZE, bvec_pool_entries, scale);

	fs_bio_set = bioset_create(BIO_POOL_SIZE, 2);

	if (!fs_bio_set)

		panic("bio: can't allocate bios\n");