Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ames!sun-barr!newstop!sun!terra!brent
From: brent%terra@Sun.COM (Brent Callaghan)
Newsgroups: comp.protocols.nfs
Subject: Re: mountd Performance under Stress
Keywords: mountd nfs performance
Message-ID: <124174@sun.Eng.Sun.COM>
Date: 5 Sep 89 21:17:59 GMT
References: <1577@dsacg3.UUCP>
Sender: news@sun.Eng.Sun.COM
Lines: 40

I made some improvements to the mountd performance for the
SunOs 4.0.3 release.  They were oriented to speeding up mounts
from a client using the automounter's "-hosts" map.  The special
situation here is that you have can have a large number of
mount requests coming in from the same client in a short period
of time but the changes should make the mountd a bit faster for
all mount requests.

- Exports caching.  Previously the mountd had to open the /etc/exports
  file and do a linear search for the exported filesystem for each
  mount request from a client.  I had the file cached as a linked list.
  The list is valid as long as a stat() of /etc/exports shows that it
  hasn't been updated (by exportfs).

- Asynchronous /etc/rmtab updating.  The mountd was changed to update
  the /etc/rmtab *after* it had sent the response containing the
  filehandle back to the client.  There's no reason why the client
  should have to wait for this file to be updated.  BTW: the /etc/rmtab
  is already cached as a linked list.  The disk file is read only when
  the mountd starts up (presumably after a crash).

- Change netgroup/hostname checking.  Given a list of
  hostnames/netgroups there's no easy way to tell whether a name
  represents a hostname or a netgroup.  The old mountd used to take
  each name one at a time first checking it as a netgroup then as a
  hostname.  This is about the most inefficient way to do this checking
  and it could take a huge amount of time if the list was big (I've
  seen exports with 100 or so names in the list).  The new code first
  checks the whole list as if it is hostnames.  This is just a bunch of
  strcmp's so it's relatively fast.  If there's no match, then it
  assumes that the list is netgroups and checks them with innetgr
  calls.  This is a whole lot faster if the list is just hostnames.


	FYI.
		Brent

Made in New Zealand -->  Brent Callaghan  @ Sun Microsystems
			 uucp: sun!bcallaghan
			 phone: (415) 336 1051