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    SubjectRe: [RFC 00/15] mm: Implement Slab Movable Objects (SMO)
    On Tue, Mar 12, 2019 at 12:09:31AM +0000, Roman Gushchin wrote:
    > On Fri, Mar 08, 2019 at 03:14:11PM +1100, Tobin C. Harding wrote:
    > > Hi,
    > >
    > > Here is a patch set implementing movable objects within the SLUB
    > > allocator. This is work based on Christopher's patch set:
    > >
    > > https://lore.kernel.org/patchwork/project/lkml/list/?series=377335
    > >
    > > The original code logic is from that set and implemented by Christopher.
    > > Clean up, refactoring, documentation, and additional features by myself.
    > > Blame for any bugs remaining falls solely with myself. Patches using
    > > Christopher's code use the Co-developed-by tag.
    > >
    > > After movable objects are implemented a number of useful features become
    > > possible. Some of these are implemented in this series, including:
    > >
    > > - Cache defragmentation.
    > >
    > > Currently the SLUB allocator is susceptible to internal
    > > fragmentation. This occurs when a large number of cached objects
    > > are allocated and then freed in an arbitrary order. As the cache
    > > fragments the number of pages used by the partial slabs list
    > > increases. This wastes memory.
    > >
    > > Patch set implements the machinery to facilitate conditional cache
    > > defragmentation (via kmem_cache_defrag()) and unconditional
    > > defragmentation (via kmem_cache_shrink()). Various sysfs knobs are
    > > provided to interact with and configure this.
    > >
    > > Patch set implements movable objects and cache defragmentation for
    > > the XArray.
    > >
    > > - Moving objects to and from a specific NUMA node.
    > >
    > > - Balancing objects across all NUMA nodes.
    > >
    > > We add a test module to facilitate playing around with movable objects
    > > and a python test suite that uses the module.
    > >
    > > Everything except the NUMA stuff was tested on bare metal, the NUMA
    > > stuff was tested with Qemu NUMA emulation.
    > >
    > > Possible further work:
    > >
    > > 1. Implementing movable objects for the inode and dentry caches.
    > >
    > > 2. Tying into the page migration and page defragmentation logic so that
    > > so far unmovable pages that are in the way of creating a contiguous
    > > block of memory will become movable. This would mean checking for
    > > slab pages in the migration logic and calling slab to see if it can
    > > move the page by migrating all objects.
    >
    >
    > Hi Tobin!
    >
    > Very interesting and promising patchset! Looking forward for inode/dentry
    > moving support, might be a big deal for allocating huge pages dynamically.

    Thanks Roman, appreciate the support. I'm working on inode and dentry
    now.

    Tobin

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