DCC build options for performance and sizing

Mark G. Thomas Mark@Misty.com
Thu Jun 17 14:43:14 UTC 2010


Gary,

On Wed, Jun 09, 2010 at 09:29:30AM -0500, Gary Mills wrote:
> On Wed, Jun 09, 2010 at 01:33:21PM +0000, Vernon Schryver wrote:
> > > From: Gary Mills <mills@cc.umanitoba.ca>
> > 
> > > The upgrade from dcc-1.3.122 (32 bit) to dcc-1.3.125 (64 bit) was
> > > flawless.  However, we now have a problem with writes from dccd
> > > saturating the disk.  The I/O bandwidth is often 100% utilized.
> > > Other processes that need to read from the disk are stalling.
> > >
> > > This is Solaris 10 5/09.  Neither `-F' nor `-f' are specified in
> > > dcc_conf.  Can I add `-f' someplace to get memory mapped I/O?  Does
> > > this have to be specified for dbclean separately?  Where's the best
> > > place?
> > 
> > If the system has enough RAM to contain the hash table of dcc_db.hash
> > and the recent part of dcc_db, then the best tactic is the work-around
> > for Solaris's lack of mmap(MAP_NOSYNC).  That -around is to move
> > dcc_db.hash (but of course not dcc_db) to a memory mapped file system.
> > /tmp is often a RAM file system on Solaris systems, so adding -H/tmp
> > to DBCLEAN_ARGS in dcc_conf should be effective.
> 
> Yes, I read about that.  I was reluctant to change so many things at
> the same time.  It's not a good idea for system processes to create
> files in /tmp because that's a publically-writable directory.
> /var/run is a better choice.  The startup script would have to create
> /var/run/dcc, for example, and make it owned by the DCC user.  I assume
> it doesn't already do that.
> 
> The servers do have sufficient memory.  I'll do some testing to see if
> `-H/var/run/dcc' solves the problem.

With 64bit Solaris-9, using /tmp has worked very well for me, and solved 
the disk I/O saturation problem. dccd is hovering around 6.6GB RAM, plus 
the 2GB for the tmpfs dcc_db.hash file.

Mark

-- 
Mark G. Thomas (Mark@Misty.com)
Web: http://mgtinternet.com/
Tel: +1-215-512-0112 US: 877-512-0112



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