Date: Tue, 3 Feb 2004 11:54:11 -0500 (EST) From: Robert Watson <rwatson@FreeBSD.org> To: Peter Edwards <peter.edwards@openet-telecom.com> Cc: current@FreeBSD.org Subject: Re: Coalescing pipe allocation Message-ID: <Pine.NEB.3.96L.1040203115210.79056E-100000@fledge.watson.org> In-Reply-To: <401FCCBE.2010008@openet-telecom.com>
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On Tue, 3 Feb 2004, Peter Edwards wrote: > I have certainly taken that at face value at least once when deciding on > how to use (or not use) pipes. Is this portability issue so > ridiculously out of date that the comment in the pipe(2) manpage should > be removed, or at least toned down? It seems silly to incur the costs of > implementation you've mentioned and then recommend that the feature not > be used. Well, I don't know so much about the portability issues, but I can say that it seems silly to incur the costs if few applications take advantage of the feature. Especially if the cost can be defered until the feature is exercised. I have some local patches that defer all pipe buffer allocation until a particular direction is first used, but this has some potential downsides, including increasing the chances that a lack of resources is discovered on first-use, rather than on allocation of the pipe (which makes it a lot harder to write robust applications). Another issue to look at is keeping a pool of buffers to amortize the cost of allocation from the pipe_map, which is something I've also started looking at. I haven't tried benchmarking the differences as yet. Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Senior Research Scientist, McAfee Research
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