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    SubjectRe: lockdep complaints in slab allocator
    On Tue, 24 Nov 2009, Peter Zijlstra wrote:

    > We should cull something, just merging more and more of them is useless
    > and wastes everybody's time since you have to add features and
    > interfaces to all of them.

    I agree, but it's difficult to get widespread testing or development
    interest in an allocator that is sitting outside of mainline. I don't
    think any allocator could suddenly be merged as the kernel default, it
    seems like a prerequisite to go through the preliminary merging and
    development. The severe netperf TCP_RR regression that slub has compared
    to slab was never found before it became the default allocator, otherwise
    there would probably have been more effort into its development as well.
    Unfortunately, slub's design is such that it will probably never be able
    to nullify the partial slab thrashing enough, even with the percpu counter
    speedup that is now available because of Christoph's work, to make TCP_RR
    perform as well as slab.

    > Then maybe we should toss SLUB? But then there's people who say SLUB is
    > better for them. Without forcing something to happen we'll be stuck with
    > multiple allocators forever.

    Slub is definitely superior in diagnostics and is a much simpler design
    than slab. I think it would be much easier to remove slub than slab,
    though, simply because there are no great slab performance degradations
    compared to slub. I think the best candidate for removal might be slob,
    however, because it hasn't been compared to slub and usage may not be as
    widespread as expected for such a special case allocator.

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      Last update: 2009-11-24 22:49    [W:3.869 / U:0.120 seconds]
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