VFS(7)

NAME
vfs - vfs layer under DragonFly

DESCRIPTION
On DragonFly all filesystems are handled through the vfs abstraction layer.

SYSCTL VARIABLES
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 vfs behavior to be modified; In this document we will only cover the ones that are generic to vfs and not specific to any of filesystems.

debug.disablecwd
    Disables the getcwd() functionality.

debug.disablefullpath
    Disables fullpath lookups.

debug.nchash
    Size of namecache hash table.

debug.nclockwarn
    Warn on locked namecache entries in ticks.

debug.ncmount_cache_enable
    Prints the status if mount point cache is enabled.

debug.ncnegfactor
    Ratio of namecache negative entries.

debug.ncp_shared_lock_disable
    Disables shared namecache locks.

debug.ncnegflush
    Batch flush negative entries.

debug.ncposflush
    Batch flush positive entries.

debug.ncposlimit
    Number of cache entries allocated.

debug.ncvp_debug
    Controls namecache debug level (0-3).

debug.numdefered
    Number of cache entries allocated.

debug.numvnodes
    Prints currently allocated vnode count.

debug.verbose_reclaims
    Outputs filename of reclaimed vnodes.

vfs.bufcache_bw
    Controls data cycling within the buffer cache.

vfs.bufspace
    Amount of memory available for buffers.

vfs.cache.numcache
    Number of namecaches entries.

vfs.cache.numleafs
    Number of namecaches entries.

vfs.cache.numneg
    Number of negative namecache entries.

vfs.check_buf_overlap
    Controls overlapping buffer checking.

vfs.debug_bufbio, vfs.debug_commit vfs.debug_kvabio
    Enables debugging of specific sub systems.

vfs.dirtybufcount
    Pending number of dirty buffers.

vfs.dirtybufcounthw
    Pending number of dirty buffers (heavy weight).

vfs.dirtybufspace
    Pending bytes of dirty buffers (all).

vfs.dirtybufspacehw
    Pending bytes of dirty buffers (heavy weight).

vfs.dirtykvaspace
    KVA reserved by dirty buffers (all).

vfs.flushperqueue
    Number of buffers to flush from each per-cpu queue.

vfs.getnewbufcalls
    New buffer header acquisition requests.

vfs.hibufspace
    Minimum amount of memory to reserve for system buffer space.

vfs.hidirtybufspace
    High watermark used to trigger explicit flushing of dirty buffers.

vfs.hirunningspace
    Sysctl determines how much outstanding write I/O may be queued to disk controllers system wide at any given instance.

vfs.lobufspace
    Minimum amount of memory to reserve for system buffer space.

vfs.lodirtybufspace
    Number of dirty buffers to flush before bufdaemon becomes inactive.

vfs.lorunningspace
    Minimum amount of buffer space required for active I/O.

vfs.lowmempgallocs
    Page allocations done during periods of very low free memory.

vfs.max_readahead
    Limit in bytes for desired cluster read-ahead.

vfs.maxbufspace
    Minimum amount of memory to reserve for system buffer space.

vfs.maxmallocbufspace
    Maximum amount of memory reserved for buffers using malloc.

vfs.nbuf
    Total number of buffers in buffer cache.

vfs.quota_enabled
    Enables vfs quota.

vfs.real_root
    Prints real root mount string.

vfs.reassignbufcalls
    Prints a number of times buffers have been reassigned to the proper list. Counter can be safely reseted back to 0.

vfs.runningbufcount
    I/O buffers currently in progress due to asynchronous writes.

vfs.runningbufspace
    I/O bytes currently in progress due to asynchronous writes.

vfs.timestamp_precision
    Controls granularity used on file timestamps.

    0   - seconds only, nanoseconds zeroed.

    1   - seconds and nanoseconds, accurate within 1/HZ.

    2   - seconds and nanoseconds, truncated to microseconds.

    3   - seconds and nanoseconds, maximum precision.

vfs.usermount
    Allows non-root users to mount filesystems.

vfs.varsym_enable
    Enables Variant Symlinks.

vfs.vm_cycle_point
    Controls active or inactive pages queue transition.

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

kern.chroot_allow_open_directories

    0 - disallowed for all processes.

    1 - allowed for processes that were not already chroot(2)'ed.

    2 - allowed for all processes.

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.

security.hardlink_check_gid
    Unprivileged processes cannot create hard links to files owned by other groups.

security.hardlink_check_uid
    Unprivileged processes cannot create hard links to files owned by other users.

SEE ALSO
autofs(5), devfs(5), ffs(5), hammer(5), tuning(7), vkernel(7), swapcache(8), sysctl(8), tunefs(8)

HISTORY
The vfs manual first appeared in DragonFly 5.1.