There are much bigger savings to be had. If you do a "ps", you'll see
we are running not one, but two copies of bash just to start the X
server.
Anyone interested should take a stab at playing with the gpe-dm display
manager for a small display manager, rather than the remains of the
amazingly overcomplex X startup to support switching desktop
environments wer are using.
In any case, remember that OOM is a reality we have to face on our
machine, so I'd rather handle it gracefully than have the system lock
up. So some conservatism is in order here.
Also, I mispoke slightly: On B3 systems (and the few systems we've
ECO'ed) the keyboard won't be powered down; standard B2 systems, the
keyboard controller is on the wrong power rail.
Regards,
- Jim
On Sun, 2007-04-01 at 21:58 +0200, Jens Axboe wrote:
> Hi,
>
> Looking over the (rarely used) block/scsi bits, we can free up ~150kb of
> kernel memory by reducing the memory tied down in memory pools. These
> are pre-allocated and basically only ever used in OOM conditions, and
> for some no longer valid reason they are sized way to aggressively. We
> only really need 1 backup, this patch plays it safe and allocates 2.
>
> I'll push this patch locally upstream as well, perhaps we can use it
> meanwhile. 150kb is quite a bit of memory, when all you have is 128MiB
> :-)
>
> diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
> index 4c2471e..d812123 100644
> --- a/drivers/md/dm-crypt.c
> +++ b/drivers/md/dm-crypt.c
> @@ -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;
> diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
> index 4eb73d3..8bdc8a8 100644
> --- a/drivers/md/dm-io.c
> +++ b/drivers/md/dm-io.c
> @@ -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;
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 3668b17..11a98df 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -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;
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 9f7482d..05d79af 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -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;
> diff --git a/fs/bio.c b/fs/bio.c
> index 7618bcb..693940d 100644
> --- a/fs/bio.c
> +++ b/fs/bio.c
> @@ -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");
>
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 08daf32..4d85262 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -276,7 +276,7 @@ extern struct bio_pair *bio_split(struct bio *bi,
> mempool_t *pool,
> extern mempool_t *bio_split_pool;
> extern void bio_pair_release(struct bio_pair *dbio);
>
> -extern struct bio_set *bioset_create(int, int, int);
> +extern struct bio_set *bioset_create(int, int);
> extern void bioset_free(struct bio_set *);
>
> extern struct bio *bio_alloc(gfp_t, int);
>
--
Jim Gettys
One Laptop Per Child
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