lkml.org 
[lkml]   [2013]   [Jan]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 2/2] mm: forcely swapout when we are out of page cache
    On Wed,  9 Jan 2013 15:21:14 +0900
    Minchan Kim <minchan@kernel.org> wrote:

    > If laptop_mode is enable, VM try to avoid I/O for saving the power.
    > But if there isn't reclaimable memory without I/O, we should do I/O
    > for preventing unnecessary OOM kill although we sacrifices power.
    >
    > One of example is that we are out of page cache. Remained one is
    > only anonymous pages, for swapping out, we needs may_writepage = 1.
    >
    > Reported-by: Luigi Semenzato <semenzato@google.com>
    > Signed-off-by: Minchan Kim <minchan@kernel.org>
    > ---
    > mm/vmscan.c | 6 ++++++
    > 1 file changed, 6 insertions(+)
    >
    > diff --git a/mm/vmscan.c b/mm/vmscan.c
    > index 439cc47..624c816 100644
    > --- a/mm/vmscan.c
    > +++ b/mm/vmscan.c
    > @@ -1728,6 +1728,12 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
    > free = zone_page_state(zone, NR_FREE_PAGES);
    > if (unlikely(file + free <= high_wmark_pages(zone))) {
    > scan_balance = SCAN_ANON;
    > + /*
    > + * From now on, we have to swap out
    > + * for peventing OOM kill although
    > + * we sacrifice power consumption.
    > + */
    > + sc->may_writepage = 1;
    > goto out;
    > }
    > }

    This is pretty ugly. get_scan_count() is, as its name implies, an
    idempotent function which inspects the state of things and returns a
    result. As such, it has no business going in and altering the state of
    the scan_control.

    We have code in both direct reclaim and in kswapd to set may_writepage
    if vmscan is getting into trouble. I don't see why adding another
    instance is necessary if the existing instances are working correctly.



    (Is it correct that __zone_reclaim() ignores laptop_mode?)


    I have a feeling that laptop mode has bitrotted and these patches are
    kinda hacking around as-yet-not-understood failures...


    \
     
     \ /
      Last update: 2013-01-10 01:41    [W:2.400 / U:0.324 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site