mirror_zfs/module
chrisrd e71cade67d Scale the dbuf cache with arc_c
Commit d3c2ae1 introduced a dbuf cache with a default size of the
minimum of 100M or 1/32 maximum ARC size. (These figures may be adjusted
using dbuf_cache_max_bytes and dbuf_cache_max_shift.) The dbuf cache
is counted as metadata for the purposes of ARC size calculations.

On a 1GB box the ARC maximum size defaults to c_max 493M which gives a
dbuf cache default minimum size of 15.4M, and the ARC metadata defaults
to minimum 16M. I.e. the dbuf cache is an significant proportion of the
minimum metadata size. With other overheads involved this actually means
the ARC metadata doesn't get down to the minimum.

This patch dynamically scales the dbuf cache to the target ARC size
instead of statically scaling it to the maximum ARC size. (The scale is
still set by dbuf_cache_max_shift and the maximum size is still fixed by
dbuf_cache_max_bytes.) Using the target ARC size rather than the current
ARC size is done to help the ARC reach the target rather than simply
focusing on the current size.

Reviewed-by: Chunwei Chen <tuxoko@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Chris Dunlop <chris@onthe.net.au>
Issue #6506 
Closes #6561
2017-09-29 15:49:19 -07:00
..
avl OpenZFS 7028 - avl_destroy_nodes supports emptying, not just destroying, an avl tree 2017-08-30 12:08:38 -07:00
icp Retire legacy test infrastructure 2017-08-15 17:26:38 -07:00
nvpair OpenZFS 2976 - remove useless offsetof() macros 2017-08-30 15:53:38 -07:00
unicode codebase style improvements for OpenZFS 6459 port 2017-01-22 13:25:40 -08:00
zcommon Native Encryption for ZFS on Linux 2017-08-14 10:36:48 -07:00
zfs Scale the dbuf cache with arc_c 2017-09-29 15:49:19 -07:00
.gitignore Improve gitignore 2017-05-25 10:14:13 -07:00
Makefile.in Retire legacy test infrastructure 2017-08-15 17:26:38 -07:00