Re: [gentoo-amd64] Re: System load during emerge

[Peter Humphrey <prh@gotadsl.co.uk>]

On Sunday 04 March 2007 16:09:03 Duncan wrote:
> Peter Humphrey <prh@gotadsl.co.uk> posted
> 200703041151.37846.prh@gotadsl.co.uk, excerpted below, on  Sun, 04 Mar
>
> > What is the machine doing?
>
> There's a couple things to check.  First, you say /tmp is on tmpfs and in
> memory (no swap), but you don't mention where you have $PORTAGE_TMPDIR
> pointed. 

It's not long since we discussed this. It's set to /tmp, and so is 
PKG_TMPDIR.

> Second, for general disk access speed (IOW, not portage specific), if
> you've not checked it, emerge hdparm if necessary and see if your hard
> drives are using DMA.  If they aren't, you'll have MUCH slower disk i/o.

Hdparm is installed and does set DMA on. The only disk access I can foresee 
portage doing is to write its log file. Could that really consume as much 
time as I'm seeing? Seems unlikely to me.

[Later...] I've now found that if I run "hdparm -d1 /dev/sda" from an X 
terminal I get "HDIO_SET_DMA failed: Inappropriate ioctl for device", but 
when /etc/init.d/hdparm is run during boot I see [ok] for each drive. Looks 
like I've got some exploring to do.

> Of course, also note that depending on the ebuild stage and how much of
> what it is accessing you already have cached, portage does do some non-
> tmp I/O access. 

As I said, I was watching firefox being compiled. All the preliminary stages 
had been completed by then. All the source code should have been in memory, 
but I can't say the same for any other libraries. On the other hand, just 
how much time is needed to load all the development libraries needed for 
this compilation?

> There's also portage logging and associated log variables.  Again, this
> shouldn't be a big deal if you've got DMA on your drives, but it might be
> if you don't.

Yes, that's the only thing I can think of.

> Finally, if it's writing anything to NFS mounts or the like over the
> network, or if you have distcc active, it's possible the wait is on the
> network, not on your local hard drives, of course depending on exactly
> how you are configured.

I did play with distcc but found it unreliable on a large package, so I've 
removed it from make.conf. I don't use NFS or any other networked 
operations that I can think of.

Thanks for the suggestions.

-- 
Rgds
Peter
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