[lkml]   [2007]   [Aug]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH 04/10] mm: slub: add knowledge of reserve pages
    On Tue, Aug 07, 2007 at 05:13:52PM -0700, Christoph Lameter wrote:
    > On Mon, 6 Aug 2007, Peter Zijlstra wrote:
    > > Restrict objects from reserve slabs (ALLOC_NO_WATERMARKS) to allocation
    > > contexts that are entitled to it.
    > Is this patch actually necessary?
    > If you are in an atomic context and bound to a cpu then a per cpu slab is
    > assigned to you and no one else can take object aways from that process
    > since nothing else can run on the cpu.

    Servicing I/O over the network requires an allocation to send a buffer
    and an allocation to later receive the acknowledgement. We can't free
    our send buffer (or the memory it's supposed to clean) until the
    relevant ack is received. We have to hold our reserves privately
    throughout, even if an interrupt that wants to do GFP_ATOMIC
    allocation shows up in-between.

    > If you are not in an atomic context and are preemptable or can switch
    > allocation context then you can create another context in which reclaim
    > could be run to remove some clean pages and get you more memory. Again no
    > need for the patch.

    By the point that this patch is relevant, there are already no clean
    pages. The only way to free up more memory is via I/O.

    Mathematics is the supreme nostalgia of our time.
    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: 2007-08-08 03:47    [W:0.027 / U:49.960 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site