Re: Alignment of disk-I/O from userland.

From: Sam Leffler (sam_at_errno.com)
Date: 10/07/03

  • Next message: Scott Long: "Re: Alignment of disk-I/O from userland." 
    To: "Poul-Henning Kamp" <phk@phk.freebsd.dk>, Scott Long <scottl@freebsd.org>
Date: Mon, 6 Oct 2003 17:53:28 -0700

    On Monday 06 October 2003 04:11 pm, Poul-Henning Kamp wrote:
    > In message <20031006163218.L55190@pooker.samsco.home>, Scott Long writes:
            ...stuff deleted...
    > >As for returning an error code for a buffer that we (arbitrarily) believe
    > >to be too big to align, [...]
    >
    > I have never advocated returning an error based on "alignment and size",
    > only based on alignment alone.

    Imposing this restriction is a major semantic change that I consider a very
    bad idea. You are basically imposing the semantics of O_DIRECT on all i/o
    operations going to a device. I think it is important to give best effort to
    support unaligned operations `by default. I can imagine restricting this to
    some upper size bound but existing applications, regardless of how well you
    consider them to be written, must continue to work.

            Sam

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  • Next message: Scott Long: "Re: Alignment of disk-I/O from userland."

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