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    SubjectRe: [RFC 8/8] Reduce inode memory usage for systems with a high MAX_NUMNODES
    On 1/16/07, Christoph Lameter <> wrote:
    > On Tue, 16 Jan 2007, Paul Menage wrote:
    > > On 1/15/07, Christoph Lameter <> wrote:
    > > >
    > > > This solution may be a bit hokey. I tried other approaches but this
    > > > one seemed to be the simplest with the least complications. Maybe someone
    > > > else can come up with a better solution?
    > >
    > > How about a 64-bit field in struct inode that's used as a bitmask if
    > > there are no more than 64 nodes, and a pointer to a bitmask if there
    > > are more than 64 nodes. The filesystems wouldn't need to be involved
    > > then, as the bitmap allocation could be done in the generic code.
    > How would we decide if there are more than 64 nodes? Runtime or compile
    > time?

    I was thinking runtime, unless MAX_NUMNODES is less than 64 in which
    case you can make the decision at compile time.

    > If done at compile time then we will end up with a pointer to an unsigned
    > long for a system with <= 64 nodes. If we allocate the nodemask via
    > kmalloc then we will always end up with a mininum allocation size of 64
    > bytes.

    Can't we get less overhead with a slab cache with appropriate-sized objects?

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      Last update: 2007-01-16 21:37    [W:0.020 / U:12.532 seconds]
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