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    SubjectRe: [patch 09/10] Remove the SLOB allocator for 2.6.23

    (added Matt to the Cc: list)

    * Christoph Lameter <clameter@sgi.com> wrote:

    > Maintenance of slab allocators becomes a problem as new features for
    > allocators are developed. The SLOB allocator in particular has been
    > lagging behind in many ways in the past:
    >
    > - Had no support for SLAB_DESTROY_BY_RCU for years (but no one
    > noticed)
    >
    > - Still has no support for slab reclaim counters. This may currently
    > not be necessary if one would restrict the supported configurations
    > for functionality relying on these. But even that has not been done.
    >
    > The only current advantage over SLUB in terms of memory savings is
    > through SLOBs kmalloc layout that is not power of two based like SLAB
    > and SLUB which allows to eliminate some memory waste.
    >
    > Through that SLOB has still a slight memory advantage over SLUB of
    > ~350k in for a standard server configuration. It is likely that the
    > savings are is smaller for real embedded configurations that have less
    > functionality.

    actually, one real advantage of the SLOB is that it is a minimal, really
    simple allocator. Its text and data size is so small as well.

    here's the size comparison:

    text data bss dec hex filename
    10788 837 16 11641 2d79 mm/slab.o
    6205 4207 124 10536 2928 mm/slub.o
    1640 44 4 1688 698 mm/slob.o

    slab/slub have roughly the same footprint, but slob is 10% of that size.
    Would be a waste to throw this away.

    A year ago the -rt kernel defaulted to the SLOB for a few releases, and
    barring some initial scalability issues (which were solved in -rt) it
    worked pretty well on generic PCs, so i dont buy the 'it doesnt work'
    argument either.

    Ingo
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