Hi,
I had a quick question about the load average calculation.
In the (cores * CPUs) calculation, is that cores per CPU or total cores
in the system? For example, if you have two quad-core processors, would
you want a load average <= 16 (8 cores * 2 CPUs) or <= 8 (4 cores * 2 CPUs)?
Thanks,
Dave
Ronny Schedel wrote:
> It depends on how many cores/CPUs you have. In the SMP world, you can run 4
> processes at 4 cores at the same time without any problem. Your load average
> is 4 or less, depending on how much load they consume.
>
> Optimum:
> load average <= cores * CPUs
>
> Overload:
> load average > cores * CPUs
>
> So, optimum for one Quad Core CPU is:
> load average <= 4 * 1
>
> This means not you can only run 4 L4D servers on one Quad Core, you have to
> look how the load is, because the servers does not run all the time, they
> take some milliseconds sleep and other processes can run. Maybe you can run
> 6 or 8.
>
>
>> Keep in mind that load average is an expression of queue depth. Some
>> types
>> of servers can handle deep queues with no visible impact shown to the end
>> user. Gameservers are not that kind of animal. They require constant,
>> nearly instantaneous updates in both directions in order to have truly
>> smooth, seamless play. In the past, any time I saw load average above one
>> I
>> saw an impact of some sort.
>>
>> A load average above 3 seems to manifest itself in L4D servers in some
>> unpredictable ways that can generally be ignored by most players.
>>
>> If you don't want to keep sending jarring notes that throw your players
>> off,
>> you really want to see your load average below 2. This should be true
>> regardless of the number of CPUs that you have in your box. Thus, my
>> comment in an earlier email about converting one of my public servers back
>> over to Steam group only. Having 2 dedicated to just the Steam group will
>> still let people fill up the public servers first and use the two
>> semi-private ones as relief.
>>
>>
>> [snip]
>>
>>
>>> ------------------------------
>>>
>>> Message: 3
>>> Date: Wed, 26 Nov 2008 17:28:11 +0100
>>> From: "Ronny Schedel" <[EMAIL PROTECTED]>
>>> Subject: Re: [hlds_linux] -fork configuration tip
>>> To: "Half-Life dedicated Linux server mailing list"
>>> <[email protected]>
>>> Message-ID: <[EMAIL PROTECTED]>
>>> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>>> reply-type=original
>>>
>>>
>>> You have only 4 cores, with a load of 8 your server is overloaded. CPU
>>> usage
>>> does not matter these days, any new multicore CPU can handle Source
>>> servers.
>>> If you want lag free and smooth servers, your load average should not
>>> exceed
>>> your amount of cores.
>>>
>>>
>>>> Our load average goes up to about 8. Given that we're running 12
>>>> instances
>>>> on a quad-core, this doesn't bother me, and certainly performance is
>>>> fine...
>>>> I've seen the blood spatter effect too, but I don't think that's
>>>> specifically performance related, it's just a glitch ;)
>>>>
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>
>
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--
Dave Parker
Utica College
Integrated Information Technology Services
(315) 792-3229
Registered Linux User #408177
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