Quick question on I/O limiter

Hi,

The io_rate can go over the refill rate, but if it does it for to long you will run out of tokens.

It is when you run out of io_tokens you will run into a problem.

The system works the same as iptables buckets

Adam

To clarify a little, you can do as much IO as you want as long as you have >0 tokens. When you get to 0, you run out, and you are limited to doing IO at a rate on average equal to refill rate,

Maybe it will also help to clear up what each number means:

io_count=25142137

I believe this is the total input/output your linode has done (since boot I think)

io_rate=166

This is how much input/output your Linode is currently doing per unit of time.

io_tokens=199933

This is basically your input/output buffer… If you're iorate is above tokenrefill, this will slowly go down. If it reaches 0, then that's when your Linode starts to get limited, and you can only use token_refill tokens per unit of time.

token_refill=512

The rate at which your io_tokens buffer is refilled per unit of time.

token_max=200000

The max size of your i/o buffer.

@tierra:

io_tokens=199933

This is basically your input/output buffer… If you're iorate is above tokenrefill, this will slowly go down. If it reaches 0, then that's when your Linode starts to get limited, and you can only use tokenrefill tokens per unit of time. So when I originally wrote "Am I right in assuming that if the iotokens value is positive then I'm not actively being limited? " then I was correct and I'm doing just fine :-)

Thanks!

@sweh:

So when I originally wrote "Am I right in assuming that if the io_tokens value is positive then I'm not actively being limited? " then I was correct and I'm doing just fine :-)

Thanks!

That's kind of a yes and no answer. If your programming something that relies on that answer, then use the assumption that if iotokens is greater than tokenrefill, then your not actively being limited. Your Linode may have just been granted another tokenrefill tokens after being in the hole, in which case, your not in the free and clear just yet. Another way to tell is to look at your iorate. If it's close to the same as tokenrefill, and your iotokens bucket is pretty empty, then your being limited.

If your going to be making assumptions on this, your safest bet would be to say if your iotokens is less than 10% of your tokenmax, then your using too much I/O.