linux-kernel - Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3

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Message-ID: <20070222145933.GA12671@elte.hu>
Date:	Thu, 22 Feb 2007 15:59:33 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	David Miller <davem@...emloft.net>
Cc:	johnpol@....mipt.ru, arjan@...radead.org, drepper@...hat.com,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	hch@...radead.org, akpm@....com.au, alan@...rguk.ukuu.org.uk,
	zach.brown@...cle.com, suparna@...ibm.com, davidel@...ilserver.org,
	jens.axboe@...cle.com, tglx@...utronix.de
Subject: Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3


* Ingo Molnar <mingo@...e.hu> wrote:

> Firstly, i dont think you are fully applying the syslet/threadlet 
> model. There is no reason why an 'idle' client would have to use up a 
> full thread! It all depends on how you use syslets/threadlets, and how 
> (frequently) you queue back requests from cachemiss threads back to 
> the primary thread. It is only the simplest queueing model where there 
> is one thread per request that is currently blocked. 
> Syslets/threadlets do /not/ force request processing to be performed 
> in the async context forever - the async thread could very much queue 
> it back to the primary context. (That's in essence what Tux did.) So 
> the same state-machine techniques can be applied on both the syslet 
> and the threadlet model, but in much more natural (and thus lower 
> overhead) points: /between/ system calls and not in the middle of 
> them. There are a number of measures that can be used to keep the 
> number of parallel threads down.

i think the best model here is to use kevents or epoll to discover 
accept()-able or recv()-able keepalive sockets, and to do the main 
request loop via syslets/threadlets, with a 'queue back to the main 
context if we went async and if the request is done' feedback mechanism 
that keeps the size of the pool down.

	Ingo
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