On Fri, May 20, 2011 at 12:19 PM, Minchan Kim <minchan.kim@xxxxxxxxx> wrote:
> On Fri, May 20, 2011 at 12:01:12PM -0400, Andrew Lutomirski wrote:
>> On Fri, May 20, 2011 at 11:33 AM, Minchan Kim <minchan.kim@xxxxxxxxx> wrote:
>>
>> > diff --git a/mm/vmscan.c b/mm/vmscan.c
>> > index 8bfd450..a5c01e9 100644
>> > --- a/mm/vmscan.c
>> > +++ b/mm/vmscan.c
>> > @@ -1430,7 +1430,10 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>> >
>> > /* Check if we should syncronously wait for writeback */
>> > if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
>> > + unsigned long nr_active;
>> > set_reclaim_mode(priority, sc, true);
>> > + nr_active = clear_active_flags(&page_list, NULL);
>> > + count_vm_events(PGDEACTIVATE, nr_active);
>> > nr_reclaimed += shrink_page_list(&page_list, zone, sc);
>> > }
>> >
>> > --
>>
>> I'm now running that patch *without* the pgdat_balanced fix or the
>> need_resched check. The VM_BUG_ON doesn't happen but I still get
>
> Please forget need_resched.
> Instead of it, could you test shrink_slab patch with !pgdat_balanced?
>
> @@ -231,8 +231,11 @@ unsigned long shrink_slab(struct shrink_control *shrink,
> if (scanned == 0)
> scanned = SWAP_CLUSTER_MAX;
>
> - if (!down_read_trylock(&shrinker_rwsem))
> - return 1; /* Assume we'll be able to shrink next time */
> + if (!down_read_trylock(&shrinker_rwsem)) {
> + /* Assume we'll be able to shrink next time */
> + ret = 1;
> + goto out;
> + }
>
> list_for_each_entry(shrinker, &shrinker_list, list) {
> unsigned long long delta;
> @@ -286,6 +289,8 @@ unsigned long shrink_slab(struct shrink_control *shrink,
> shrinker->nr += total_scan;
> }
> up_read(&shrinker_rwsem);
> +out:
> + cond_resched();
> return ret;
> }
>
>> incorrect OOM kills.
>>
>> However, if I replace the check with:
>>
>> if (false &&should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
>>
>> then my system lags under bad memory pressure but recovers without
>> OOMs or oopses.
>
> I agree you can see OOM but oops? Did you see any oops?
No oops. I've now reproduced the OOPS with both the if (false) change
and the clear_active_flags change.
Also, would this version be better? I think your version overcounts
nr_scanned, but I'm not sure what effect that would have.
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3f44b81..d1dabc9 100644
@@ -1426,8 +1437,13 @@ shrink_inactive_list(unsigned long nr_to_scan,
struct zone *zone,
/* Check if we should syncronously wait for writeback */
if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
+ unsigned long nr_active, old_nr_scanned;
set_reclaim_mode(priority, sc, true);
+ nr_active = clear_active_flags(&page_list, NULL);
+ count_vm_events(PGDEACTIVATE, nr_active);
+ old_nr_scanned = sc->nr_scanned;
nr_reclaimed += shrink_page_list(&page_list, zone, sc);
+ sc->nr_scanned = old_nr_scanned;
}
local_irq_disable();
I just tested 2.6.38.6 with the attached patch. It survived dirty_ram
and test_mempressure without any problems other than slowness, but
when I hit ctrl-c to stop test_mempressure, I got the attached oom.
--Andy
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test.patch
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oom.txt.xz
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