[lkml]   [2001]   [Oct]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: pre6 VM issues
    On Tue, Oct 09, 2001 at 11:34:47AM -0200, Marcelo Tosatti wrote:
    > The problem may well be in the memory balancing Andrea, but I'm not trying
    > to hide it with the infinite loop.

    I assumed fixing the oom faliures with highmem was the main reason of
    the infinite loop.

    > The infinite loop is just a guarantee that we'll have a reliable way of
    > throttling the allocators which can block. Not doing the infinite loop is

    Throttling have nothing to do with the infinite loop.

    > just way too fragile IMO and it is _prone_ to fail in intensive
    > loads.

    It is too fragile if the vm is doing the wrong actions and so we must
    loop over and over again before it finally does the right thing.

    If allocation fails that's a nice feedback that tell us "the memory
    balancing is at least inefficient in doing the right thing, looping
    would only waste more cache and more time for the allocation".

    Think a list where pages can be only freeable or unfreeable. Now scan
    _all_ the pages and free all the freeable ones. Finished. If it failed
    and it couldn't free anything it means there was nothing to free so
    we're oom. How can that be "fragile"?

    In real life it isn't as simple as that, there's some "race" effect
    caming from the schedules in between, there are multiple lists, there's
    swapout etc... so it's a little more complex than just "freeable" and
    "unfreeable" and a single list, but it can be done, 2.2 does that too,
    if we loop over and over again and we do no progress in the right
    direction I prefer to know about that via an allocation faliure rather
    than by just getting sucking performance. Also an allocation faliure is
    a minor problem compared to a deadlock that the infinite loop cannot

    > If the problem is the highmem balancing, I'll love to get your fixes and
    > integrate with the infinite loop logic, which is a separated (related,
    > yes, but separate) thing.

    The infinite loop shouldn't do anything except introducing the deadlock
    after that (otherwise it means I failed :), but you're free to go in
    your direction if you think it's the right one of course (like I'm free
    to go in my direction since I think it's the right one).

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2005-03-22 13:05    [W:0.044 / U:79.064 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site