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    SubjectRe: [RFC] Limit the size of the IPV4 route hash.
    Robin Holt <holt@sgi.com> wrote:
    >
    > > The big risk is that someone has a too-small table for some specific
    > > application and their machine runs more slowly than it should, but they
    > > never notice. I wonder if it would be possible to put a little once-only
    > > printk into the routing code: "warning route-cache chain exceeded 100
    > > entries: consider using the rhash_entries boot option".
    >
    > Since the hash gets flushed every 10 seconds, what if we kept track of
    > the maximum depth reached and when we reach a certain threshold, just
    > allocate a larger hash and replace the old with the new. I do like the
    > printk idea so the admin can prevent inconsistent performance early in
    > the run cycle for the system. We could even scale the hash size up based
    > upon demand.

    Once the system has been running for a while, the possibility of allocating
    a decent number of physically-contiguous pages is basically zero.

    If we were to dynamically size it we'd need to either use new data
    structure (slower) or use vmalloc() (slower and can fragment vmalloc
    space).
    -
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