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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: Fri, 27 Sep 2024 09:59:16 -0400
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On 9/26/2024 10:36 PM, Lawrence D'Oliveiro wrote:
> On Thu, 26 Sep 2024 22:17:29 -0400, Arne Vajhøj wrote:
>> On 9/26/2024 9:26 PM, Lawrence D'Oliveiro wrote:
>>> That and the need for all the ASTs.
>>
>> Why should AST's be a problem?
>>
>> The "call this function when task is done" approach is a very common
>> design today. DEC was ahead of time with that.
> 
> Set attention AST → wait for AST to trigger → queue actual I/O → wait for
> AST to signal completion. Too many system calls and transitions back and
> forth between user and kernel modes.

I don't think anyone would use that flow.

You setup a read attention AST, it triggers and then you know that
there are data to be read. There is no reason to make reading async
then, because you know it will not block.

Arne