Commit 3d8aab2d authored Oct 03, 2014 by Junichi Nomura Committed by Mike Snitzer Oct 05, 2014

dm: use bioset_create_nobvec()



Since DM core uses bio_clone_fast() for both bio-based and request-based
DM devices there is no need for DM's bioset to have a bvec mempool.

With this patch, on arch with 4KB page for example, memory usage will be
reduced by 64KB for each bio-based DM device and 1MB for each
request-based DM device.

For example, when you create 10,000 bio-based DM devices and 1,000
request-based DM devices, memory usage of biovec under no load is:
  # grep biovec /proc/slabinfo

  biovec-256        418068 418068   4096  ...
  biovec-128             0      0   2048  ...
  biovec-64              0      0   1024  ...
  biovec-16              0      0    256  ...

With this patch series applied, the usage becomes:
  # grep biovec /proc/slabinfo

  biovec-256           116    116   4096  ...
  biovec-128             0      0   2048  ...
  biovec-64              0      0   1024  ...
  biovec-16              0      0    256  ...

So 4096 * (418068 - 116) = 1.6GB of memory is saved in this example.

Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

parent 99778273

drivers/md/dm.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2895,7 +2895,7 @@ struct dm_md_mempools *dm_alloc_md_mempools(unsigned type, unsigned integrity, u
		if (!pools->io_pool)
		goto out;

		pools->bs = bioset_create(pool_size, front_pad);
		pools->bs = bioset_create_nobvec(pool_size, front_pad);
		if (!pools->bs)
		goto out;

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