oplocks and file caching

Mac mac at ngo.org.uk
Sat Jan 31 12:54:57 GMT 1998

Hi all,

In IRIX (5.x and 6.x) there's an interesting posibility for (at least
partially) addressing the UNIX-side problems with op-locks.

There exists a mechanims known as 'fam' which uses a kernel level device to
track file changes efficiently

A user-land process can express interest in a file, and will recieve
notification when that file changes.

Here followeth the main man-page.

FAM(1M)                                                                FAM(1M)

     fam - file alteration monitor

     /usr/etc/fam [ -t NFS polling interval ]

     Fam is a server that tracks changes to the file system and relays these
     changes to interested applications.  Applications such as WorkSpace(1G)
     and Mailbox(1G) present an up-to-date view of the file system.  In the
     absence of fam, these applications and others like them would be forced
     to poll the file system to detect changes.  Fam is considerably more

     Applications can request fam to monitor any files or directories in the
     file system.  When fam detects changes to these files, it notifies the
     appropriate application.  Fam(3X) provides a programmatic interface to

     Fam is informed of file system changes as they happen by the IRIX kernel
     through the imon(1M) pseudo device driver.  Currently, fam servers do not
     communicate with each other and consequently, they poll to determine the
     state of NFS mounted file systems.  The -t option specifies the polling
     interval in seconds.  The default polling interval is 3 seconds.  Since
     fam is invoked by inetd(1M), you must edit the /etc/inetd.conf file to
     change the polling interval.

     imon(1M), fam(3X), inetd(1M), workspace(1G), mailbox(1G)

                                                                        Page 1

If anyone is interested in the API (fam(3X)) then I'll gladly send it to them.
(It's several pages so I'll not send it to the list).

          Assistant Systems Adminstrator @nibsc.ac.uk
                        dmccann at nibsc.ac.uk
   Work: +44 1707 654753 x 285     Everything else: +44 956 237670 (anytime)

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