lkml.org 
[lkml]   [2007]   [Oct]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: OOM notifications
    Andrew Morton wrote:
    > On Thu, 18 Oct 2007 16:15:31 -0400
    > Marcelo Tosatti <marcelo@kvack.org> wrote:
    >
    >> Hi,
    >>
    >> AIX contains the SIGDANGER signal to notify applications to free up some
    >> unused cached memory:
    >>
    >> http://www.ussg.iu.edu/hypermail/linux/kernel/0007.0/0901.html
    >>
    >> There have been a few discussions on implementing such an idea on Linux,
    >> but nothing concrete has been achieved.
    >>
    >> On the kernel side Rik suggested two notification points: "about to
    >> swap" (for desktop scenarios) and "about to OOM" (for embedded-like
    >> scenarios).
    >>
    >> With that assumption in mind it would be necessary to either have two
    >> special devices for notification, or somehow indicate both events
    >> through the same file descriptor.
    >>
    >> Comments are more than welcome.
    >
    > Martin was talking about some mad scheme wherin you'd create a bunch of
    > pseudo files (say, /proc/foo/0, /proc/foo/1, ..., /proc/foo/9) and each one
    > would become "ready" when the MM scanning priority reaches 10%, 20%, ...
    > 100%.
    >
    > Obviously there would need to be a lot of abstraction to unhook a permanent
    > userspace feature from a transient kernel implementation, but the basic
    > idea is that a process which wants to know when the VM is getting into the
    > orange zone would select() on the file "7" and a process which wants to
    > know when the VM is getting into the red zone would select on file "9".
    >
    > It get more complicated with NUMA memory nodes and cgroup memory
    > controllers.

    We ended up not doing that, but making a scanner that saw what
    percentage of the LRU was touched in the last n seconds, and
    printing that to userspace to deal with.

    Turns out priority is a horrible metric to use for this - it
    stays at default for ages, then falls off a cliff far too
    quickly to react to.

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-10-26 23:09    [W:7.325 / U:0.160 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site