Re: [PATCH -v2 0/9] mm: make movable onlining suck less

[Michal Hocko]

On Tue 11-04-17 13:01:43, Michal Hocko wrote:
> On Tue 11-04-17 11:59:31, Igor Mammedov wrote:
> > On Tue, 11 Apr 2017 11:23:07 +0200
> > Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> > 
> > > On Tue 11-04-17 08:38:34, Igor Mammedov wrote:
> > > > for issue2:
> > > > -enable-kvm -m 2G,slots=4,maxmem=4G -smp 4 -numa node -numa node \
> > > > -drive if=virtio,file=disk.img -kernel bzImage -append 'root=/dev/vda1' \
> > > > -object memory-backend-ram,id=mem1,size=256M -object memory-backend-ram,id=mem0,size=256M \
> > > > -device pc-dimm,id=dimm1,memdev=mem1,slot=1,node=0 -device pc-dimm,id=dimm0,memdev=mem0,slot=0,node=1  
> > > 
> > > I must be doing something wrong here...
> > > qemu-system-x86_64 -enable-kvm -monitor telnet:127.0.0.1:9999,server,nowait -net nic -net user,hostfwd=tcp:127.0.0.1:5555-:22 -serial file:test.qcow_serial.log -enable-kvm -m 2G,slots=4,maxmem=4G -smp 4 -numa node -numa node -object memory-backend-ram,id=mem1,size=256M -object memory-backend-ram,id=mem0,size=256M -device pc-dimm,id=dimm1,memdev=mem1,slot=1,node=0 -device pc-dimm,id=dimm0,memdev=mem0,slot=0,node=1 -drive file=test.qcow,if=ide,index=0
> > > 
> > > for i in $(seq 0 3)
> > > do
> > > 	sh probe_memblock.sh $i
> > > done
> >
> > dimm to node mapping comes from ACPI subsystem (_PXM object in memory device),
> > which adds memory blocks automatically on hotplug.
> 
> Hmm, memory_probe_store relies on memory_add_physaddr_to_nid which in
> turn relies on numa_meminfo. I am not familiar with the intialization
> and got lost in in the code rather quickly but I assumed this should get
> the proper information from the ACPI subsystem. I will have to double
> check.
> 
> > you probably don't have ACPI_HOTPLUG_MEMORY config option enabled.
> 
> Yes that is the case and enabling it made all 4 memblocks available
> and associated with the proper node
> # ls -l /sys/devices/system/memory/memory3?/node*
> lrwxrwxrwx 1 root root 0 Apr 11 12:56 /sys/devices/system/memory/memory32/node0 -> ../../node/node0
> lrwxrwxrwx 1 root root 0 Apr 11 12:56 /sys/devices/system/memory/memory33/node0 -> ../../node/node0
> lrwxrwxrwx 1 root root 0 Apr 11 12:56 /sys/devices/system/memory/memory34/node1 -> ../../node/node1
> lrwxrwxrwx 1 root root 0 Apr 11 12:56 /sys/devices/system/memory/memory35/node1 -> ../../node/node1
> 
> # grep . /sys/devices/system/memory/memory3?/valid_zones
> /sys/devices/system/memory/memory32/valid_zones:Normal Movable
> /sys/devices/system/memory/memory33/valid_zones:Normal Movable
> /sys/devices/system/memory/memory34/valid_zones:Normal Movable
> /sys/devices/system/memory/memory35/valid_zones:Normal Movable
> 
> I can even reproduce your problem
> # echo online_movable > /sys/devices/system/memory/memory33/state
> # echo online > /sys/devices/system/memory/memory32/state
> # grep . /sys/devices/system/memory/memory3?/valid_zones
> /sys/devices/system/memory/memory32/valid_zones:Movable
> /sys/devices/system/memory/memory33/valid_zones:Movable
> /sys/devices/system/memory/memory34/valid_zones:Normal Movable
> /sys/devices/system/memory/memory35/valid_zones:Normal Movable
> 
> I will investigate this

Dang, guess what. It is a similar type bug I've fixed in
show_valid_zones [1] already.

[1] http://lkml.kernel.org/r/20170410152228.GF4618@xxxxxxxxxxxxxx
---
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index ec2f987ec549..410c7ccb74fb 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -541,7 +541,7 @@ static inline bool zone_intersects(struct zone *zone,
 {
 	if (zone->zone_start_pfn <= start_pfn && start_pfn < zone_end_pfn(zone))
 		return true;
-	if (start_pfn + nr_pages > start_pfn && !zone_is_empty(zone))
+	if (start_pfn + nr_pages > zone->zone_start_pfn && !zone_is_empty(zone))
 		return true;
 	return false;
 }

I have decided to make it more readable and did zone_is_empty check
first. Everything is in my git tree attempts/rewrite-mem_hotplug branch.
I have to test it but I believe this is the culprit here.
-- 
Michal Hocko
SUSE Labs