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.Dd February 17, 2018
.Dt VFS 7
.Os
.Sh NAME
.Nm vfs
.Nd vfs layer under DragonFly
.Sh DESCRIPTION
On
.Dx
all filesystems are handled through the
.Nm
abstraction layer.
.Sh SYSCTL VARIABLES
.Xr sysctl 8
variables permit system behavior to be monitored and controlled at run-time.
Some sysctls simply report on the behavior of the system; others allow
the
.Nm
behavior to be modified;
In this document we will only cover the ones that are generic to
.Nm
and not specific to any of filesystems.
.Bl -tag -width "xxxxxx"
.It Va debug.disablecwd
Disables the
.Fn getcwd
functionality.
.It Va debug.disablefullpath
Disables fullpath lookups.
.It Va debug.nchash
Size of namecache hash table.
.It Va debug.nclockwarn
Warn on locked namecache entries in ticks.
.It Va debug.ncmount_cache_enable
Prints the status if mount point cache is enabled.
.It Va debug.ncnegfactor
Ratio of namecache negative entries.
.It Va debug.ncp_shared_lock_disable
Disables shared namecache locks.
.It Va debug.ncnegflush
Batch flush negative entries.
.It Va debug.ncposflush
Batch flush positive entries.
.It Va debug.ncposlimit
Number of cache entries allocated.
.It Va debug.ncvp_debug
Controls namecache debug level (0-3).
.It Va debug.numdefered
Number of cache entries allocated.
.It Va debug.numvnodes
Prints currently allocated vnode count.
.\" XXX CTLFLAG_RD is this a tunable?
.It Va debug.verbose_reclaims
Outputs filename of reclaimed vnodes.
.It Va vfs.bufcache_bw
Controls data cycling within the buffer cache.
.It Va vfs.bufspace
Amount of memory available for buffers.
.It Va vfs.cache.numcache
Number of namecaches entries.
.It Va vfs.cache.numcwdcalls
Number of current directory resolution calls.
.It Va vfs.cache.numcwdfailnf
Number of current directory failures due to lack of file.
.It Va vfs.cache.numcwdfailsz
Number of current directory failures due to large result.
.It Va vfs.cache.numcwdfound
Number of current directory resolution successes.
.It Va vfs.cache.numleafs
Number of namecaches entries.
.It Va vfs.cache.numneg
Number of negative namecache entries.
.It Va vfs.check_buf_overlap
Controls overlapping buffer checking.
.It Va vfs.debug_bufbio , Va vfs.debug_commit Va vfs.debug_kvabio
Enables debugging of specific sub systems.
.It Va vfs.dirtybufcount
Pending number of dirty buffers.
.It Va vfs.dirtybufcounthw
Pending number of dirty buffers (heavy weight).
.It Va vfs.dirtybufspace
Pending bytes of dirty buffers (all).
.It Va vfs.dirtybufspacehw
Pending bytes of dirty buffers (heavy weight).
.It Va vfs.dirtykvaspace
KVA reserved by dirty buffers (all).
.It Va vfs.flushperqueue
Number of buffers to flush from each per-cpu queue.
.It Va vfs.getnewbufcalls
New buffer header acquisition requests.
.It Va vfs.hibufspace
Minimum amount of memory to reserve for system buffer space.
.It Va vfs.hidirtybufspace
High watermark used to trigger explicit flushing of dirty buffers.
.It Va vfs.hirunningspace
Sysctl determines how much outstanding write I/O may be queued to
disk controllers system wide at any given instance.
.It Va vfs.lobufspace
Minimum amount of memory to reserve for system buffer space.
.It Va vfs.lodirtybufspace
Number of dirty buffers to flush before bufdaemon becomes inactive.
.It Va vfs.lorunningspace
Minimum amount of buffer space required for active I/O.
.It Va vfs.lowmempgallocs
Page allocations done during periods of very low free memory.
.It Va vfs.max_readahead
Limit in bytes for desired cluster read-ahead.
.It Va vfs.maxbufspace
Minimum amount of memory to reserve for system buffer space.
.It Va vfs.maxmallocbufspace
Maximum amount of memory reserved for buffers using malloc.
.It Va vfs.nbuf
Total number of buffers in buffer cache.
.It Va vfs.quota_enabled
Enables
.Nm
quota.
.It Va vfs.real_root
Prints real root mount string.
.It Va vfs.reassignbufcalls
Prints a number of times buffers have been reassigned to the proper list.
Counter can be safely reseted back to 0.
.It Va vfs.runningbufcount
I/O buffers currently in progress due to asynchronous writes.
.It Va vfs.runningbufspace
I/O bytes currently in progress due to asynchronous writes.
.It Va vfs.timestamp_precision
Controls granularity used on file timestamps.
.Bl -tag -width "X"
.It 0
- seconds only, nanoseconds zeroed.
.It 1
- seconds and nanoseconds, accurate within 1/HZ.
.It 2
- seconds and nanoseconds, truncated to microseconds.
.It 3
- seconds and nanoseconds, maximum precision.
.El
.It Va vfs.usermount
Allows non-root users to mount filesystems.
.It Va vfs.varsym_enable
Enables Variant Symlinks.
.It Va vfs.vm_cycle_point
Controls active or inactive pages queue transition.
.It Va vfs.write_behind
Sysctl defaults to 1 (on).
This tells the filesystem to issue media writes as full clusters are collected,
which typically occurs when writing large sequential files.
vfs.write_behind_minfilesize
.It Va kern.chroot_allow_open_directories
.Bl -tag -width "X"
.It 0 - disallowed for all processes.
.It 1 - allowed for processes that were not already chroot(2)'ed.
.It 2 - allowed for all processes.
.El
.It Va kern.maxvnodes
Specifies how many vnodes and related file structures the kernel will cache.
The kernel uses a very generous default for this parameter based on
available physical memory.
.It Va security.hardlink_check_gid
Unprivileged processes cannot create hard links to files owned by other groups.
.It Va security.hardlink_check_uid
Unprivileged processes cannot create hard links to files owned by other users.
.El
.Sh SEE ALSO
.Xr autofs 5 ,
.Xr devfs 5 ,
.Xr ffs 5 ,
.Xr hammer 5 ,
.Xr tuning 7 ,
.Xr vkernel 7 ,
.Xr swapcache 8 ,
.Xr sysctl 8 ,
.Xr tunefs 8
.Sh HISTORY
The
.Nm
manual first appeared in
.Dx 5.1 .