• Re: Microkernels & Capabilities (was Re: Byte ordering)

    From Lawrence D'Oliveiro@21:1/5 to Paul A. Clayton on Fri Oct 18 05:54:33 2024
    On Wed, 16 Oct 2024 11:34:31 -0400, Paul A. Clayton wrote:

    While the argument that only microkernels can provide modularity with
    respect to software development seems highly flawed, modularity with
    respect to privilege seems more challenging (impossible?) for a
    monolithic kernel and modularity with respect to fault isolation seems
    to require substantially more discipline/ constraint than typical for a monolithic design.

    The CHERI project has been trying to revive the capability concept. They
    chose BSD over Linux (neither being microkernel-based) for their research purely on the basis that BSD was a slower-moving target. (Maybe they
    didn’t know about LTS Linux kernels.)

    Seems like the idea of using a microkernel never occurred to them. Not seriously, anyway.

    Software like FUSE (Filesystem in Userspace) hints that some microkernel aspects are desirable even in a monolithic kernel system.

    It is useful for less performance-intensive code. For example, NTFS
    support has primarily been primarily provided over the past couple of
    decades via FUSE; the equivalent kernel-based filesystem module has been lagging somewhat in features, even though that is still seen as the better approach for high performance.

    Obviously this is not true of Linux filesystems in general, it just
    happens to be the case with NTFS.

    I know relatively little about OSes, but the arguments I have read on
    both sides seem to have been very biased.

    Can’t argue with reality, though.

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