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Disable vdev cache (readahead) by default.

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The vdev cache is very underutilized (hit ratio 30%-70%) and may consume
excessive memory on systems with many vdevs.

Illumos-gate revision:	13346

Obtained from:	Illumos (Bug #175)
MFC after:	1 week
This commit is contained in:
Martin Matuska 2011-06-28 06:32:35 +00:00
parent 855c382417
commit 85a418012f
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=223622
1 changed files with 8 additions and 1 deletions
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9
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_cache.c
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@ -71,9 +71,16 @@
* 1<<zfs_vdev_cache_bshift byte reads by the vdev_cache (aka software
* track buffer). At most zfs_vdev_cache_size bytes will be kept in each
* vdev's vdev_cache.
*
* TODO: Note that with the current ZFS code, it turns out that the
* vdev cache is not helpful, and in some cases actually harmful. It
* is better if we disable this. Once some time has passed, we should
* actually remove this to simplify the code. For now we just disable
* it by setting the zfs_vdev_cache_size to zero. Note that Solaris 11
* has made these same changes.
*/
int zfs_vdev_cache_max = 1<<14; /* 16KB */
int zfs_vdev_cache_size = 10ULL << 20; /* 10MB */
int zfs_vdev_cache_size = 0;
int zfs_vdev_cache_bshift = 16;
#define VCBS (1 << zfs_vdev_cache_bshift) /* 64KB */