DragonFly commits List (threaded) for 2011-04
git: HAMMER VFS - Implement swapcache for HAMMER data in double_buffer mode
Author: Matthew Dillon <firstname.lastname@example.org>
Date: Sat Apr 2 17:16:15 2011 -0700
HAMMER VFS - Implement swapcache for HAMMER data in double_buffer mode
* Support swapcache data caching when HAMMER's double_buffer mode is enabled.
Typically the following sysctls:
vm.swapcache.use_chflags=0 (optional - see man swapcache)
* This causes swapcache to attempt to cache file data from HAMMER
filesystems stored via the block device instead of the individual
* This allows swapcache to more efficiently cache file data without
vnode recycling from a limited kern.maxvnodes value getting in the way.
If you have a large dataset spread across many smaller files which would
normally overwhelm maxvnodes, and even on large systems handling very
large data sets where you wish to cache the file data for some of the
files (using use_chflags=1 mode), this makes it possible to cache ALL
the file data AND meta-data on the SSD even though the related vnodes
cached by the kernel get recycled.
* Whereas it may have been inefficient to turn on vm.swapcache.data_enable
before, due to filesystem scans and such, it may now be possible to this
feature on with double buffering also enabled.
Note that you must still be cognizant of the aggregate amount of file
data being accessed by your system if you have set use_chflags to 0, you
simply no longer need to worry about how many files that data belongs to.
* Enabling HAMMER's double_buffer mode will reduce performance somewhat for
the normal best-case file caching, but it will also greatly improve
performance once you start blowing out your memory caches.
Summary of changes:
sys/vfs/hammer/hammer_btree.c | 7 ++++++-
sys/vfs/hammer/hammer_cursor.h | 1 +
sys/vfs/hammer/hammer_object.c | 2 ++
sys/vfs/hammer/hammer_reblock.c | 1 +
sys/vfs/hammer/hammer_vnops.c | 24 ++++++++++++++++++++++++
5 files changed, 34 insertions(+), 1 deletions(-)
DragonFly BSD source repository