RE: [squid-users] Strange performance effects on squid during off peak hours

On Wed, 15 Sep 2010 20:53:04 +0100, Martin Sperl <Martin.Sperl_at_amdocs.com>
wrote:
> Hi Amos!
>
> Thanks for your feedback.
>
>> Squid is still largely IO event driven. If the network IO is less than
>> say 3-4 req/sec Squid can have a queue of things waiting to happen
which
>> get delayed a long time (hundreds of ms) waiting to be kicked off.
>> Your overview seems to show that behaviour clearly.
>>
>> There have been some small improvements and fixes to several of the
>> lagging things but I think its still there in even the latest Squid.
>
> Here the Hit/s statistics on this specific server for the time:
> +------+-------+-------+
> | h | allHPS| cssART|
> +------+-------+-------+
> | 0 | 48.34 | 0.016 |
> | 1 | 49.80 | 0.015 |
> | 2 | 49.01 | 0.015 |
> | 3 | 47.08 | 0.018 |
> | 4 | 17.34 | 0.024 |
> | 5 | 4.00 | 0.042 |
> | 6 | 0.52 | 0.054 |
> | 7 | 9.02 | 0.034 |
> | 8 | 7.18 | 0.038 |
> | 9 | 8.25 | 0.035 |
> | 10 | 9.45 | 0.034 |
> | 11 | 14.71 | 0.030 |
> | 12 | 23.94 | 0.023 |
> | 13 | 31.04 | 0.021 |
> | 14 | 35.02 | 0.020 |
> | 15 | 38.87 | 0.019 |
> | 16 | 40.92 | 0.019 |
> | 17 | 43.39 | 0.017 |
> | 18 | 45.62 | 0.016 |
> | 19 | 47.58 | 0.017 |
> | 20 | 51.91 | 0.014 |
> | 21 | 53.65 | 0.014 |
> | 22 | 40.87 | 0.016 |
> | 23 | 47.40 | 0.016 |
> +------+-------+-------+
>
> So to summarize it: we need to keep the number of hits above 30 hits/s
for
> squid, so that we get an acceptable Response time.
>
> I believe it will need some convincing of management to get this
> assumption tested in production ;)
>
> One other Question: is squid 3.1 "better" in this respect than 3.0?

Than 3.0? I believe so. Though have no data on it.
The upper req/sec cap where the most effort has gone is 15%-20% higher, I
have not done any serious testing like this with the lower limits before.

If you are able to it would be very enlightening and helpful for many I
think.

Amos
Received on Wed Sep 15 2010 - 23:02:32 MDT