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

    On Mon, 9 Jul 2007, Pekka Enberg wrote:
    > > I assume with "slab external fragmentation" you mean allocating a
    > > whole page for a slab when there are not enough objects to fill the
    > > whole thing thus wasting memory? We could try to combat that by
    > > packing multiple variable-sized slabs within a single page. Also,
    > > adding some non-power-of-two kmalloc caches might help with internal
    > > fragmentation.

    On Mon, 9 Jul 2007, Christoph Lameter wrote:
    > Ther are already non-power-of-two kmalloc caches for 96 and 192 bytes
    > sizes.

    I know that, but for my setup at least, there seems to be a need for a
    non-power of two cache between 512 and 1024. What I am seeing is average
    allocation size for kmalloc-512 being around 270-280 which wastes total
    of 10 KB of memory due to internal fragmentation. Might be a buggy caller
    that can be fixed with its own cache too.

    On Mon, 9 Jul 2007, Pekka Enberg wrote:
    > > In any case, SLUB needs some serious tuning for smaller machines
    > > before we can get rid of SLOB.

    On Mon, 9 Jul 2007, Christoph Lameter wrote:
    > Switch off CONFIG_SLUB_DEBUG to get memory savings.

    Curious, /proc/meminfo immediately after boot shows:

    SLUB (debugging enabled):

    (none):~# cat /proc/meminfo
    MemTotal: 30260 kB
    MemFree: 22096 kB

    SLUB (debugging disabled):

    (none):~# cat /proc/meminfo
    MemTotal: 30276 kB
    MemFree: 22244 kB


    (none):~# cat /proc/meminfo
    MemTotal: 30280 kB
    MemFree: 22004 kB

    That's 92 KB advantage for SLUB with debugging enabled and 240 KB when
    debugging is disabled.

    Nick, Matt, care to retest SLUB and SLOB for your setups?

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      Last update: 2007-07-10 10:21    [W:0.021 / U:12.656 seconds]
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