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    SubjectRe: [00/41] Large Blocksize Support V7 (adds memmap support)
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    Andrea Arcangeli <andrea@suse.de> writes:

    > On Mon, Sep 17, 2007 at 12:56:07AM +0200, Goswin von Brederlow wrote:
    >> When has free ever given any usefull "free" number? I can perfectly
    >> fine allocate another gigabyte of memory despide free saing 25MB. But
    >> that is because I know that the buffer/cached are not locked in.
    >
    > Well, as you said you know that buffer/cached are not locked in. If
    > /proc/meminfo would be rubbish like you seem to imply in the first
    > line, why would we ever bother to export that information and even
    > waste time writing a binary that parse it for admins?

    As a user I know it because I didn't put a kernel source into /tmp. A
    programm can't reasonably know that.

    >> On the other hand 1GB can instantly vanish when I start a xen domain
    >> and anything relying on the free value would loose.
    >
    > Actually you better check meminfo or free before starting a 1G of Xen!!

    Xen has its own memory pool and can quite agressively reclaim memory
    from dom0 when needed. I just ment to say that the number in
    /proc/meminfo can change in a second so it is not much use knowing
    what it said last minute.

    >> The only sensible thing for an application concerned with swapping is
    >> to whatch the swapping and then reduce itself. Not the amount
    >> free. Although I wish there were some kernel interface to get a
    >> preasure value of how valuable free pages would be right now. I would
    >> like that for fuse so a userspace filesystem can do caching without
    >> cripling the kernel.
    >
    > Repeated drop caches + free can help.

    I would kill any programm that does that to find out how much free ram
    the system has.

    MfG
    Goswin
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