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Re: [PATCH 0/6] mm: make movable onlining suck less

From Mel Gorman <mgorman@suse.de>
Newsgroups linux.kernel
Subject Re: [PATCH 0/6] mm: make movable onlining suck less
Date 2017-04-06 19:00 +0200
Message-ID <ttiVj-3pQ-5@gated-at.bofh.it> (permalink)
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On Thu, Apr 06, 2017 at 06:21:55PM +0200, Michal Hocko wrote:
> > This was my first time using your git branch instead of applying the patches
> > from this thread to v4.11-rc5 myself.
> 
> OK, so this looks like another thing to resolve. I have seen this
> warning as well but I didn't consider it relevant because I had to tweak
> the code make the node go offline (removed check_and_unmap_cpu_on_node
> from try_offline_node) so I thought it was a fallout from there. 
> 
> But let's have a look. hotadd_new_pgdat does for an existing pgdat
> 		/* Reset the nr_zones, order and classzone_idx before reuse */
> 		pgdat->nr_zones = 0;
> 		pgdat->kswapd_order = 0;
> 		pgdat->kswapd_classzone_idx = MAX_NR_ZONES;
> 
> so free_area_init_node absolutely has to hit this warning. This is not
> in the Linus tree because it is still in Andrew's mmotm coming from
> http://www.ozlabs.org/~akpm/mmotm/broken-out/mm-vmscan-prevent-kswapd-sleeping-prematurely-due-to-mismatched-classzone_idx.patch
> 
> So yay, finally that doesn't come from me. Mel, I guess that either
> hotadd_new_pgdat should keep its kswapd_classzone_idx = 0 or the warning
> should be updated.
> 

Actually, it's obvious very quickly when I started the fix that updating
the warning would then trigger on normal boot. It's more appropriate to
let a hotadd of a new pgdat defer the initialisation of that field to
kswapd starting for the new node.

Can you try this? It's build/boot tested only, no hotplug testing.

---8<---
mm, vmscan: prevent kswapd sleeping prematurely due to mismatched classzone_idx -fix

The patch "mm, vmscan: prevent kswapd sleeping prematurely due to mismatched
classzone_idx" has different initial starting conditions when kswapd
is asleep. kswapd initialises it properly when it starts but the patch
initialises kswapd_classzone_idx early and trips on a warning in
free_area_init_node. This patch leaves the kswapd_classzone_idx as zero
and defers to kswapd to initialise it properly when it starts.

This is a fix to the mmotm patch
mm-vmscan-prevent-kswapd-sleeping-prematurely-due-to-mismatched-classzone_idx.patch

Signed-off-by: Mel Gorman <mgorman@suse.de>

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 2309a7fbec93..76d4745513ee 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1214,10 +1214,14 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
 
 		arch_refresh_nodedata(nid, pgdat);
 	} else {
-		/* Reset the nr_zones, order and classzone_idx before reuse */
+		/*
+		 * Reset the nr_zones, order and classzone_idx before reuse.
+		 * Note that kswapd will init kswapd_classzone_idx properly
+		 * when it starts in the near future.
+		 */
 		pgdat->nr_zones = 0;
 		pgdat->kswapd_order = 0;
-		pgdat->kswapd_classzone_idx = MAX_NR_ZONES;
+		pgdat->kswapd_classzone_idx = 0;
 	}
 
 	/* we can use NODE_DATA(nid) from here */

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Thread

[PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-03-30 14:00 +0200
  [PATCH 1/6] mm: get rid of zone_is_initialized Michal Hocko <mhocko@kernel.org> - 2017-03-30 14:00 +0200
    Re: [PATCH 1/6] mm: get rid of zone_is_initialized "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2017-03-31 05:50 +0200
      Re: [PATCH 1/6] mm: get rid of zone_is_initialized Michal Hocko <mhocko@kernel.org> - 2017-03-31 08:50 +0200
        Re: [PATCH 1/6] mm: get rid of zone_is_initialized Michal Hocko <mhocko@kernel.org> - 2017-03-31 08:50 +0200
    [PATCH v1 1/6] mm: get rid of zone_is_initialized Michal Hocko <mhocko@kernel.org> - 2017-03-31 09:50 +0200
      Re: [PATCH v1 1/6] mm: get rid of zone_is_initialized Michal Hocko <mhocko@kernel.org> - 2017-04-05 10:20 +0200
        Re: [PATCH v1 1/6] mm: get rid of zone_is_initialized Michal Hocko <mhocko@kernel.org> - 2017-04-05 11:30 +0200
        Re: [PATCH v1 1/6] mm: get rid of zone_is_initialized Igor Mammedov <imammedo@redhat.com> - 2017-04-05 11:50 +0200
  [PATCH 2/6] mm, tile: drop arch_{add,remove}_memory Michal Hocko <mhocko@kernel.org> - 2017-03-30 14:00 +0200
  [PATCH 3/6] mm: remove return value from init_currently_empty_zone Michal Hocko <mhocko@kernel.org> - 2017-03-30 14:00 +0200
    Re: [PATCH 3/6] mm: remove return value from init_currently_empty_zone "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2017-03-31 06:00 +0200
      Re: [PATCH 3/6] mm: remove return value from  init_currently_empty_zone Michal Hocko <mhocko@kernel.org> - 2017-03-31 08:50 +0200
        Re: [PATCH 3/6] mm: remove return value from init_currently_empty_zone "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2017-03-31 09:10 +0200
          Re: [PATCH 3/6] mm: remove return value from  init_currently_empty_zone Michal Hocko <mhocko@kernel.org> - 2017-03-31 09:20 +0200
    Re: [PATCH 3/6] mm: remove return value from  init_currently_empty_zone Michal Hocko <mhocko@kernel.org> - 2017-03-31 09:50 +0200
    Re: [PATCH 3/6] mm: remove return value from  init_currently_empty_zone Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-03 23:30 +0200
      Re: [PATCH 3/6] mm: remove return value from  init_currently_empty_zone Michal Hocko <mhocko@kernel.org> - 2017-04-04 09:40 +0200
  [PATCH 6/6] mm, memory_hotplug: remove unused cruft after memory hotplug rework Michal Hocko <mhocko@kernel.org> - 2017-03-30 14:00 +0200
    Re: [PATCH 6/6] mm, memory_hotplug: remove unused cruft after memory  hotplug rework Michal Hocko <mhocko@kernel.org> - 2017-03-31 09:50 +0200
  Re: [PATCH 0/6] mm: make movable onlining suck less Heiko Carstens <heiko.carstens@de.ibm.com> - 2017-03-31 21:20 +0200
    Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-03 09:40 +0200
  Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-03 14:00 +0200
    Re: [PATCH 0/6] mm: make movable onlining suck less Igor Mammedov <imammedo@redhat.com> - 2017-04-03 14:30 +0200
    Re: [PATCH 0/6] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-03 22:00 +0200
      Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-03 22:30 +0200
        Re: [PATCH 0/6] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-03 22:50 +0200
          Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-04 09:30 +0200
            Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-04 09:40 +0200
              Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-04 10:30 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-04 18:00 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-04 18:10 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-04 18:50 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-04 20:40 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-04 21:50 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-04 23:50 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-05 08:50 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-05 11:30 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-05 17:00 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-05 17:50 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-05 19:40 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-05 20:20 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-05 21:50 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-05 23:10 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-06 13:10 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-05 18:00 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-05 18:40 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-05 23:00 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-06 11:30 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-05 16:00 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-05 17:30 +0200
                Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-05 08:40 +0200
  Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-06 15:10 +0200
    Re: [PATCH 0/6] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-06 17:30 +0200
      Re: [PATCH 0/6] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-06 17:50 +0200
        Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-06 18:30 +0200
          Re: [PATCH 0/6] mm: make movable onlining suck less Mel Gorman <mgorman@suse.de> - 2017-04-06 18:30 +0200
          Re: [PATCH 0/6] mm: make movable onlining suck less Mel Gorman <mgorman@suse.de> - 2017-04-06 19:00 +0200
            Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-06 19:20 +0200
              Re: [PATCH 0/6] mm: make movable onlining suck less Mel Gorman <mgorman@suse.de> - 2017-04-06 19:50 +0200
      Re: [PATCH 0/6] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-06 17:50 +0200

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