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    SubjectRe: [PATCH] Making i/dhash_entries cmdline work as it use to.
    On 07/13/04 05:29:13, David Howells wrote:
    >
    > Jose R. Santos <jrsantos@austin.ibm.com> wrote:
    > > Also, any particular reason why MAX_SYS_HASH_TABLE_ORDER was set to 14?
    > > I am already seeing the need to go higher on my 64GB setup and was
    > > wondering if this could be bumped up to 19.
    >
    > Yes. IBM did some testing and found that was about optimal. No significant
    > gain was found with anything greater.

    On a single setup. What about people that want to use Linux on a 128way with
    over a terabyte of memory. Certainly ORDER 14 might be to small for them.

    > > I'm sending a patch that get the cmdline options working as the did before
    > > where the could override the kernel calculations and increases
    > > MAX_SYS_HASH_TABLE_ORDER to 19. Only tested on PPC64 at the moment.
    >
    > You need to be careful increasing the maximum order - you have to remember
    > that this affects several tables (well, at least two at the moment), and so
    > the effect is multiplied.

    Only if I use the cmdline option. With no command line arguments this allocate
    the kernels sain calculated defaults.

    > It may be reasonable to let the kernel cmdline override the maximum number of
    > buckets calculated on the scaling factor provided to the function (effectively
    > number of buckets per unit memory), but consider that the number of objects
    > that can be allocated and linked into the table is in effect governed by such
    > a factor.

    It seems easier to specify a the number of buckets you want than specifying a
    scaling factor, which some people may have problems figuring out.

    -JRS
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