On Sat, Mar 05, 2011 at 06:34:37PM +0300, Andrew Vagin wrote:
> On 03/05/2011 06:20 PM, Minchan Kim wrote:
> >On Sat, Mar 05, 2011 at 02:44:16PM +0300, Andrey Vagin wrote:
> >>Check zone->all_unreclaimable in all_unreclaimable(), otherwise the
> >>kernel may hang up, because shrink_zones() will do nothing, but
> >>all_unreclaimable() will say, that zone has reclaimable pages.
> >>
> >>do_try_to_free_pages()
> >> shrink_zones()
> >> for_each_zone
> >> if (zone->all_unreclaimable)
> >> continue
> >> if !all_unreclaimable(zonelist, sc)
> >> return 1
> >>
> >>__alloc_pages_slowpath()
> >>retry:
> >> did_some_progress = do_try_to_free_pages(page)
> >> ...
> >> if (!page&& did_some_progress)
> >> retry;
> >>
> >>Signed-off-by: Andrey Vagin<avagin@xxxxxxxxxx>
> >>---
> >> mm/vmscan.c | 2 ++
> >> 1 files changed, 2 insertions(+), 0 deletions(-)
> >>
> >>diff --git a/mm/vmscan.c b/mm/vmscan.c
> >>index 6771ea7..1c056f7 100644
> >>--- a/mm/vmscan.c
> >>+++ b/mm/vmscan.c
> >>@@ -2002,6 +2002,8 @@ static bool all_unreclaimable(struct zonelist *zonelist,
> >>
> >> for_each_zone_zonelist_nodemask(zone, z, zonelist,
> >> gfp_zone(sc->gfp_mask), sc->nodemask) {
> >>+ if (zone->all_unreclaimable)
> >>+ continue;
> >> if (!populated_zone(zone))
> >> continue;
> >> if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
> >
> >zone_reclaimable checks it. Isn't it enough?
> I sent one more patch [PATCH] mm: skip zombie in OOM-killer.
> This two patches are enough.
Sorry if I confused you.
I mean zone->all_unreclaimable become true if !zone_reclaimable in balance_pgdat.
zone_reclaimable compares recent pages_scanned with the number of zone lru pages.
So too many page scanning in small lru pages makes the zone to unreclaimable zone.
In all_unreclaimable, we calls zone_reclaimable to detect it.
It's the same thing with your patch.
> >Does the hang up really happen or see it by code review?
> Yes. You can reproduce it for help the attached python program. It's
> not very clever:)
> It make the following actions in loop:
> 1. fork
> 2. mmap
> 3. touch memory
> 4. read memory
> 5. munmmap
It seems the test program makes fork bombs and memory hogging.
If you applied this patch, the problem is gone?
>
> >>--
> >>1.7.1
> >>
> >>--
> >>To unsubscribe, send a message with 'unsubscribe linux-mm' in
> >>the body to majordomo@xxxxxxxxxx For more info on Linux MM,
> >>see: http://www.linux-mm.org/ .
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> >>Don't email:<a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx</a>
>
> import sys, time, mmap, os
> from subprocess import Popen, PIPE
> import random
>
> global mem_size
>
> def info(msg):
> pid = os.getpid()
> print >> sys.stderr, "%s: %s" % (pid, msg)
> sys.stderr.flush()
>
>
>
> def memory_loop(cmd = "a"):
> """
> cmd may be:
> c: check memory
> else: touch memory
> """
> c = 0
> for j in xrange(0, mem_size):
> if cmd == "c":
> if f[j<<12] != chr(j % 255):
> info("Data corruption")
> sys.exit(1)
> else:
> f[j<<12] = chr(j % 255)
>
> while True:
> pid = os.fork()
> if (pid != 0):
> mem_size = random.randint(0, 56 * 4096)
> f = mmap.mmap(-1, mem_size << 12, mmap.MAP_ANONYMOUS|mmap.MAP_PRIVATE)
> memory_loop()
> memory_loop("c")
> f.close()
--
Kind regards,
Minchan Kim
--
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