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    SubjectRe: 2.6.20-ck1
    Date
    Andrew Morton writes:

    > On Sun, 18 Feb 2007 08:00:06 +1100 Con Kolivas <kernel@kolivas.org> wrote:
    >
    >> On Sunday 18 February 2007 05:45, Chuck Ebbert wrote:
    >> ...
    >> > But the one I like, mm-filesize_dependant_lru_cache_add.patch,
    >> > has an on-off switch.
    >> >
    >>
    >> ...
    >>
    >> Do you still want this patch for mainline?...
    >
    > Don't think so. The problems I see are:
    >
    > - It's a system-wide knob. In many situations this will do the wrong
    > thing. Controlling pagecache should be per-process.
    >
    > - Its heuristics for working out when to invalidate the pagecache will be
    > too much for some situations and too little for others.
    >
    > - Whatever we do, there will be some applications in some situations
    > which are hurt badly by changes like this: they'll do heaps of extra IO.
    >
    >
    > Generally, the penalties for getting this stuff wrong are very very high:
    > orders of magnitude slowdowns in the right situations. Which I suspect
    > will make any system-wide knob ultimately unsuccessful.

    Rest assured I wasn't interested in pushing this patch for mainline anyway.

    -ck users can also rest assured about this patch for the following reasons:

    - The usage pattern on a desktop will guarantee that this patch helps 99.9%
    of the time rather than hurts. Therefore, this feature is enabled by default
    on -ck.

    - With the usage pattern on a server of any sort, it will be unknown whether
    this patch helps or harms. Therefore, this feature is disabled by default on
    -cks.

    --
    -ck

    -
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