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    SubjectRe: [RFC] Disk shock protection (revisited)
    On Thu, Feb 28, 2008 at 6:13 AM, Alan Cox <> wrote:
    > > > That sounds like a non starter. What if the box is busy, what if the
    > > > daemon or something you touch needs memory and causes paging ?
    > >
    > > The daemon runs mlock'd anyway, so there won't be any need for paging
    > mlock does not guarantee anything of that form. A syscall by an mlocked
    > process which causes a memory allocation can cause paging of another
    > process on the system.
    > > there. As for responsiveness under heavy load, I'm not quite sure I get
    > > your meaning. On my system, at least, the only way I have managed to
    > > decrease responsiveness noticeably is to cause a lot of I/O operations
    > It depends a lot on hardware but you can certainly get user space delays
    > in seconds as an extreme worst case.

    I don't know the details, but I believe the Linux-HA heartbeat daemons
    take significant effort to eliminate unexpected delays. See

    Lars Marowsky-Bree of Novell is extremely involved in the project and
    he at least occasionally posts on LKML. I've cc'ed him.

    Greg Freemyer
    Litigation Triage Solutions Specialist
    First 99 Days Litigation White Paper -

    The Norcross Group
    The Intersection of Evidence & Technology

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