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    SubjectIdea for improving linux buffer cache behaviour
    Forgive me if this has already been thought of, or is obsolete, or is just
    plain a bad idea, but here it is:

    When I am doing large block device operations, such as ripping a DVD, the
    cache gets loaded with all this data I don't care about (the contents of the
    DVD itself). The cache data I care about is glibc, other shared libraries, and
    binary executables like xterm + whatnot that I am constantly using. After
    doing the large block operations, all that important data is no longer in the
    cache, so it has to be reloaded from disk. It is then annoyingly slow to use
    the machine for a while, especially each new executable that has to be loaded.
    Performance is so much better when the stuff is sitting there in a ram cache.

    Here's the idea: For each cache item, keep a count of how many times it has
    been accessed (read). Also keep a count of how old the cache entry is. When
    looking for cache data to free up to make space for a new cache entry, throw
    out the data based on
    1) Lowest access count looked at first to toss
    2) If access counts equal, throw out oldest first

    Actually you could have a "keep" rating on each cache entry. The higher the
    rating the more you want to keep it in the cache. It could be this:
    A * (access_count) - B * (age)
    where A and B are positive numbers. Every time you go to cache something new
    you increment a counter and store that in with the cache entry. The age of
    the cache entry is the current value of the counter minus the cache entry's
    value. A could be much larger than B.

    The net result is commonly used items you very much want to remain in cache
    always quickly get rated very highly as the system is used.

    I'm using 2.4.20. Maybe 2.[5|6] does much more intelligent cache handling.

    PS cc me on replies, I don't read this group normally.
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