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    SubjectRe: Deadlock possibly caused by too_many_isolated.
    On Tue, Oct 19, 2010 at 11:21:45AM +0800, Shaohua Li wrote:
    > On Tue, Oct 19, 2010 at 11:09:29AM +0800, Minchan Kim wrote:
    > > On Tue, Oct 19, 2010 at 12:05 PM, Wu Fengguang <fengguang.wu@intel.com> wrote:
    > > > On Tue, Oct 19, 2010 at 10:52:47AM +0800, Minchan Kim wrote:
    > > >> Hi Wu,
    > > >>
    > > >> On Tue, Oct 19, 2010 at 11:35 AM, Wu Fengguang <fengguang.wu@intel.com> wrote:
    > > >> >> @@ -2054,10 +2069,11 @@ rebalance:
    > > >> >>                 goto got_pg;
    > > >> >>
    > > >> >>         /*
    > > >> >> -        * If we failed to make any progress reclaiming, then we are
    > > >> >> -        * running out of options and have to consider going OOM
    > > >> >> +        * If we failed to make any progress reclaiming and there aren't
    > > >> >> +        * many parallel reclaiming, then we are unning out of options and
    > > >> >> +        * have to consider going OOM
    > > >> >>          */
    > > >> >> -       if (!did_some_progress) {
    > > >> >> +       if (!did_some_progress && !too_many_isolated_zone(preferred_zone)) {
    > > >> >>                 if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
    > > >> >>                         if (oom_killer_disabled)
    > > >> >>                                 goto nopage;
    > > >> >
    > > >> > This is simply wrong.
    > > >> >
    > > >> > It disabled this block for 99% system because there won't be enough
    > > >> > tasks to make (!too_many_isolated_zone == true). As a result the LRU
    > > >> > will be scanned like mad and no task get OOMed when it should be.
    > > >>
    > > >> If !too_many_isolated_zone is false, it means there are already many
    > > >> direct reclaiming tasks.
    > > >> So they could exit reclaim path and !too_many_isolated_zone will be true.
    > > >> What am I missing now?
    > > >
    > > > Ah sorry, my brain get short circuited.. but I still feel uneasy with
    > > > this change. It's not fixing the root cause and won't prevent too many
    > > > LRU pages be isolated. It's too late to test too_many_isolated_zone()
    > > > after direct reclaim returns (after sleeping for a long time).
    > > >
    > >
    > > Intend to agree.
    > > I think root cause is a infinite looping in too_many_isolated holding FS lock.
    > > Would it be simple that too_many_isolated would be bail out after some try?
    > I'm wondering if we need too_many_isolated_zone logic. The do_try_to_free_pages
    > will return progress till all zones are unreclaimable. Assume before this we
    > don't oomkiller. If the direct reclaim fails but has progress, it will sleep.
    Not sure if this is clear. What I mean is we can delete too_many_isolated_zone,
    do_try_to_free_pages can still return 1 till all zones are unreclaimable. Before
    this direct reclaim will not oom, because it sees progress and will call congestion_wait
    to sleep. Am I missing anything?
    --
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