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

From: Ingo Molnar
Date: Wed Feb 21 2007 - 18:36:10 EST

* Michael K. Edwards <medwards.linux@xxxxxxxxx> wrote:

> 4) AIO vsyscalls whose semantics resemble those of IEEE 754 floating
> point operations, with a clear distinction between a) pipeline state
> vs. operands, b) results vs. side effects, and c) coding errors vs.
> not-a-number results vs. exceptions that cost you a pipeline flush and
> nonlocal branch.

threadlets (and syslets) are parallel contexts and they behave so -
queuing and execution semantics are then ontop of that, implemented
either by glibc, or implemented by the application. There is no
'pipeline' of requests imposed - the structure of pending requests is
totally free-form. For example in threadlet-test.c i've in essence
implemented a 'set of requests' with the submission site only interested
in whether all requests are done or not - but any stricter (or even
looser) semantics and ordering can be used too.

in terms of AIO, the best queueing model is i think what the kernel uses
internally: freely ordered, with barrier support. (That is equivalent to
a "queue of sets", where the queue are the barriers, and the sets are
the requests within barriers. If there is no barrier pending then
there's just one large freely-ordered set of requests.)

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