Date: Thu, 26 Aug 2004 07:33:05 +0200 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Scott Long <scottl@freebsd.org> Cc: arch@freebsd.org Subject: Re: potential re change for 5.3? Message-ID: <51730.1093498385@critter.freebsd.dk> In-Reply-To: Your message of "Wed, 25 Aug 2004 15:45:12 MDT." <412D0868.9060203@freebsd.org>
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In message <412D0868.9060203@freebsd.org>, Scott Long writes: >I'm not suggesting anything different, just making a note of something >that might be desirable in the future. In a way, I see GEOM as having >the potential to be like Netgraph where it intercepts operations that it >wants to process through it's framework and lets ones that it doesn't >pass directly through without a decoupling through extra kernel threads. >But that's only one possible strategy. Introducing the concept of a >I/O scheduler that spawns KSE's to handle individual I/O requests is >another possibility. Well, the problem here is that requests which cannot be dealt with due to resource shortages should be queued at the level where they require least resources. A request queued inside a driver holds far more resources than a request in the pure bio format at the entrance to the driver for instance. And spawning KSE's in low memory situations is a recipe for suicide. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
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