kernel-ark/Documentation/filesystems/9p.txt
Eric Van Hensbergen e03abc0c96 9p: implement optional loose read cache
While cacheing is generally frowned upon in the 9p world, it has its
place -- particularly in situations where the remote file system is
exclusive and/or read-only.  The vacfs views of venti content addressable
store are a real-world instance of such a situation.  To facilitate higher
performance for these workloads (and eventually use the fscache patches),
we have enabled a "loose" cache mode which does not attempt to maintain
any form of consistency on the page-cache or dcache.  This results in over
two orders of magnitude performance improvement for cacheable block reads
in the Bonnie benchmark.  The more aggressive use of the dcache also seems
to improve metadata operational performance.

Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
2007-02-18 10:16:10 -06:00

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v9fs: Plan 9 Resource Sharing for Linux
=======================================
ABOUT
=====
v9fs is a Unix implementation of the Plan 9 9p remote filesystem protocol.
This software was originally developed by Ron Minnich <rminnich@lanl.gov>
and Maya Gokhale <maya@lanl.gov>. Additional development by Greg Watson
<gwatson@lanl.gov> and most recently Eric Van Hensbergen
<ericvh@gmail.com>, Latchesar Ionkov <lucho@ionkov.net> and Russ Cox
<rsc@swtch.com>.
USAGE
=====
For remote file server:
mount -t 9p 10.10.1.2 /mnt/9
For Plan 9 From User Space applications (http://swtch.com/plan9)
mount -t 9p `namespace`/acme /mnt/9 -o proto=unix,uname=$USER
OPTIONS
=======
proto=name select an alternative transport. Valid options are
currently:
unix - specifying a named pipe mount point
tcp - specifying a normal TCP/IP connection
fd - used passed file descriptors for connection
(see rfdno and wfdno)
uname=name user name to attempt mount as on the remote server. The
server may override or ignore this value. Certain user
names may require authentication.
aname=name aname specifies the file tree to access when the server is
offering several exported file systems.
cache=mode specifies a cacheing policy. By default, no caches are used.
loose = no attempts are made at consistency,
intended for exclusive, read-only mounts
debug=n specifies debug level. The debug level is a bitmask.
0x01 = display verbose error messages
0x02 = developer debug (DEBUG_CURRENT)
0x04 = display 9p trace
0x08 = display VFS trace
0x10 = display Marshalling debug
0x20 = display RPC debug
0x40 = display transport debug
0x80 = display allocation debug
rfdno=n the file descriptor for reading with proto=fd
wfdno=n the file descriptor for writing with proto=fd
maxdata=n the number of bytes to use for 9p packet payload (msize)
port=n port to connect to on the remote server
noextend force legacy mode (no 9p2000.u semantics)
uid attempt to mount as a particular uid
gid attempt to mount with a particular gid
afid security channel - used by Plan 9 authentication protocols
nodevmap do not map special files - represent them as normal files.
This can be used to share devices/named pipes/sockets between
hosts. This functionality will be expanded in later versions.
RESOURCES
=========
Our current recommendation is to use Inferno (http://www.vitanuova.com/inferno)
as the 9p server. You can start a 9p server under Inferno by issuing the
following command:
; styxlisten -A tcp!*!564 export '#U*'
The -A specifies an unauthenticated export. The 564 is the port # (you may
have to choose a higher port number if running as a normal user). The '#U*'
specifies exporting the root of the Linux name space. You may specify a
subset of the namespace by extending the path: '#U*'/tmp would just export
/tmp. For more information, see the Inferno manual pages covering styxlisten
and export.
A Linux version of the 9p server is now maintained under the npfs project
on sourceforge (http://sourceforge.net/projects/npfs). There is also a
more stable single-threaded version of the server (named spfs) available from
the same CVS repository.
There are user and developer mailing lists available through the v9fs project
on sourceforge (http://sourceforge.net/projects/v9fs).
News and other information is maintained on SWiK (http://swik.net/v9fs).
Bug reports may be issued through the kernel.org bugzilla
(http://bugzilla.kernel.org)
For more information on the Plan 9 Operating System check out
http://plan9.bell-labs.com/plan9
For information on Plan 9 from User Space (Plan 9 applications and libraries
ported to Linux/BSD/OSX/etc) check out http://swtch.com/plan9
STATUS
======
The 2.6 kernel support is working on PPC and x86.
PLEASE USE THE KERNEL BUGZILLA TO REPORT PROBLEMS. (http://bugzilla.kernel.org)