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From: =?UTF-8?Q?Arne_Vajh=C3=B8j?= <arne@vajhoej.dk>
Newsgroups: comp.os.vms
Subject: Re: Apache + mod_php performance
Date: Mon, 30 Sep 2024 21:25:20 -0400
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On 9/30/2024 9:10 PM, Dave Froble wrote:
> On 9/30/2024 8:33 PM, Arne Vajhøj wrote:
>> On 9/30/2024 8:24 PM, Lawrence D'Oliveiro wrote:
>>> On Mon, 30 Sep 2024 19:50:38 -0400, Arne Vajhøj wrote:
>>>> On 9/29/2024 11:15 PM, Lawrence D'Oliveiro wrote:
>>>>> On Sun, 29 Sep 2024 22:34:04 -0400, Arne Vajhøj wrote:
>>>>>> But I am pretty sure that it will not work on VMS.
>>>>>
>>>>> That’s what I figured. VMS, like Windows, really wants you to use
>>>>> threads.
>>>>
>>>> For massive parallel processing on VMS then threads not
>>>> processes is the way to go.
>>>
>>> Threads require shared memory, though. Processes allow you to have a mix
>>> of shared and private data, plus the use of IPC mechanisms like message
>>> passing. This makes for a looser coupling, which better suits the way
>>> massively parallel systems are built.
>>
>> It is undeniable that multiple processes are more loosely coupled
>> than multiple threads.
>>
>> But efficiency is a problem. VMS does not do fork. Process creation
>> is expensive on VMS. None of that fancy moving descriptors over
>> Unix socket stuff.
>>
>> VMS got plenty of methods for IPC. A solution with a fixed number
>> of processes doing IPC between each other may work fine.
>>
>> But the concept of constantly starting new processes and killing
>> old processes is not going to perform great.

> Well, now, that is a rather bold statement.

Sometimes I make such.

:-)

> Granted, starting up a new process involves some overhead.
> 
> But it really depends upon the requirements.  The more use out of a 
> process once it is started, the better overall performance.  If a group 
> of worker processes is started once, then used for many tasks, then that 
> overhead happens only once.  Perhaps once a day, week, month, and even 
> year.  There are various communication methods available on VMS.
> 
> In the end, it comes down to the requirements.  An engineer must 
> evaluate the task(s) and determine what methods will give adequate results.

There are obviously a scale.

But the Apache case is to start with 5 processes, start 145 new
processes in a few seconds and then kill 140 again after maybe
30-45 seconds. And repeat.

Arne