DCC build options for performance and sizing

Gary Mills mills@cc.umanitoba.ca
Fri Jun 18 14:11:34 UTC 2010


On Thu, Jun 17, 2010 at 10:43:14AM -0400, Mark G. Thomas wrote:
> 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.
> > > 
> > > 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.
> > 
> > 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.

Yes, it's similar here under Solaris 10.  Here's part of the prstat
output on a quiet day:

     PID USERNAME  SIZE   RSS STATE  PRI NICE      TIME  CPU PROCESS/NLWP
    1547 daemon   5387M 3359M sleep   59    0   2:16:52 0.1% dccd/1
    1546 daemon    780M  456M sleep   59    0   0:10:38 0.0% dccd/1
    1345 daemon     27M   24M sleep   59    0   3:38:09 0.0% dccm/172
    1180 daemon     18M   15M sleep   59    0   1:28:54 0.0% opendkim/173
     344 daemon   2996K 1412K sleep   59    0   0:04:55 0.0% rpcbind/1
    2647 daemon   3808K 1784K sleep   59    0   0:01:42 0.0% dns-helper/1
     795 daemon   3808K 2148K sleep   59    0   0:00:05 0.0% dns-helper/1
    2620 daemon   3808K 1764K sleep   59    0   0:01:41 0.0% dns-helper/1
  ...
  Total: 32 processes, 386 lwps, load averages: 1.62, 1.52, 1.41

-- 
-Gary Mills-        -Unix Group-        -Computer and Network Services-



More information about the DCC mailing list

Contact vjs@rhyolite.com by mail or use the form.