I'm relatively new to Linode, and see the load on host34 going
over 5 with regular frequency, and over 10 or 12 at times. Is this
the normal load on a Linode server? It seems excessive, and my
Python scripts are running much slower that I had anticipated.

When this happens AFAIK I can't get the 1/20th of a server
minimum I understood was the least I would receive from a
Linode. I cannot tell if host34 is a dual CPU server, certainly
if it is not then making it one should be seriously considered IMHO.

Is User Mode Linux so new that it still has wrinkles to be worked out?

James Phillips
http://zunzun.com on host34

cat /proc/swaps might be a good place to start:

Filename                     Type            Size    Used    Priority
/dev/ubd/1                      partition       525304  204996  -1

That's over 200M in swap!

-Chris

So, when I want to see host34's load I should look at the amount
of swap space used on my linode? That doesn't make sense to me.
I have been using the load average on the first line of output from
the top command, which can show high load factors even when my
apparent CPU usage is very low. I thought swap space was related
to memory usage - is that incorrect? I'm no Joe Linux so it could be.

James Phillips, newbie at large
http://zunzun.com

Swap usage means disk usage. Every time a page gets swapped back into (or out of) RAM, you're using I/O.

I/O is one of the scarce resources on Linode, much scarcer than CPU. Caker has implemented a token scheme to make I/O fair. You can check you statistics by examining /proc/io_status.

When a process on Linux is blocked waiting for I/O, it takes up a full 1.0 on the CPU usage. That's why, I believe, you're seeing high "CPU load".

"loadavg" and "top" inside your Linode give the load of your Linode itself. When you see a high loadavg, it usually means processes are blocked, waiting for the disk. Each process blocked adds 1 to loadavg.

Having so much in swap means you're over-extending the memory of your Linode itself, causing much of the processes you are running to swap out to disk.

You should investigate placing limits on Apache threads and memory usage, mysql's memory usage, etc.

-Chris

Now *there's* advice a Linode newbie like me can sink his teeth
into! Thanks for explaining it to me, that does make sense.

James Phillips
now ju-u-u-st a bit less of a newbie

[quote="caker"]"loadavg" and "top" inside your Linode give the load of your Linode itself. When you see a high loadavg, it usually means processes are blocked, waiting for the disk. Each process blocked adds 1 to loadavg.[/quote]

I've been watching my Linode now that I understand this. Very
interesting and enlightening, and I can rewrite some of the site
to take the I/O limiting into account with good effect, I think.

May I ask why token_max is set to 20000 on my linode? From
what I gather poking around on the forums, it is because of the
swap size on my linode - is that correct? If so, reducing swap
usage should bump this number up?

James Phillips

Low token_max is down to excessive disk i/o usage, so your problem has been swap usage, not swap size per se.

I don't think upward changes to token_max occur automatically. When I got into the situation you're in now, I had to raise a ticket to get caker to set my token_max back to the original value.

The defaults are token_refill=512 and token_max=400000.

_________________
/ Peter

My understanding is if you reboot you will get your io tokens back...

Really? I was in that situation recently and got Caker to bail me out. I didn't try rebooting, though; that would be much easier! If it works please post here.

This is true when you shutdown and reboot your linode you IO is nolonger being used so it would go back up. Chris CAN give you a higher IO_MAX and ip_Refill rate for temp. if you have a good reason he has for me in the past

Well, Linode support was certainly kind and increased token_max
when I asked in a support ticket. I was asked not to thrash the
hard drive on host34 else it would have to be reduced, and this
seems perfectly reasonable.

I am curious about Gentoo re-syncing and updating: my guess
is that the host would be least busy on a Sunday, so that would
be the best time for this. It would likely make for a good bit of
swap space usage though. Any recommendations?

James Phillips

I run Gentoo on a Linode 64 (stage 1 install, not caker's distro) and I have only run into trouble (too much swapping - token_max and token_refill reduced - Linode slowed to a crawl) when linking glibc. I still had all my other services running at the same time (a little light apache, postfix and courier-imap) so I was being a bit greedy. This has been discussed here, and the advice from that discussion was to change your /etc/make.conf:

MAKEOPTS="-j1"

_________________
/ Peter

I'll try the "-j1" this weekend on my Gentoo sync and check it.
Thank you for the advice.

James Phillips

If possible, it's also a good idea with Gentoo to shutdown as many services as possible during updates. If you have a 64, you'll want at least 20-25MB of ram free before starting your updates. It's less of a problem on a 96 depending on what your running. Just remember, the more ram you have free, the less your Linode needs to dip into swap, and the less I/O it's actually going to do copying pages from ram to swap and back.