cvs commit: src/sys/nfsclient nfs_vnops.c

[Kris Kennaway]

On Sun, Oct 15, 2006 at 12:37:28PM +1000, Bruce Evans wrote:
> On Sun, 15 Oct 2006, Rink Springer wrote:
> 
> >On Sat, Oct 14, 2006 at 07:25:12AM +0000, Bruce Evans wrote:
> >>  Log:
> >>  Don't do null Setattr RPCs for VA_MARK_ATIME.  When we added the
> >>...
> >>  This is the smallest and easiest to fix of several bugs that have
> >>  increased the number of RPCs for kernel builds on nfs by more than
> >>  100% since 2004-11-05.  The real-time increase depends on network
> >>...
> 
> >The code in RELENG_6 looks as if it would benefit from this change as
> >well. Do you have a MFC planned in the nearby future?
> 
> Maybe after the larger performance bugs are fixed.  See a thread in
> freebsd-fs.
> 
> It would also be good to reduce nfs RPCs generally and there seems to
> be a lot more scope to do this for Access ones, at least by automatically
> configuring cases when a large timeout is safe.
> 
> -current and RELENG_6 still have a bogus default of 2 for nfs_access_cache
> in /etc/defaults/rc.conf, and rc.conf(5) still confusingly claims that
> setting this to a value of 2-10 seconds will substantially reduce
> network traffic.  In fact the default is 60 and smaller nonzero settings
> substantially increase network traffic; a setting of 2 is normally
> made by the rc system, and settings of 3-10 only reduce network traffic
> not so substantially by moving back towards the system default.  Settings
> of 2-10 substantially increase network traffic relative to the system
> default.

> ISTR a discussion of fixing this in rc.conf, but nothing seems to have been
> committed.  The setting is confusing in the kernel too:

----------------------------
revision 1.285
date: 2006/05/24 00:06:14;  author: kris;  state: Exp;  lines: +1 -1
Increase the nfs access cache timeout from 2 to 60.  The latter is a
more appropriate value and is also the default set by the kernel.  I
could not find a justification of why rc.conf began overriding it back
in 1998.

This dramatically cuts NFS traffic on e.g. a busy system with NFS root.

Reviewed by:    mohans
MFC After:      2 weeks
----------------------------

Kris
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