Re: [PATCH v2 3/6] mm/memory_hotplug: Process all zones when removing memory

2019-08-30 Thread Michal Hocko
On Fri 30-08-19 09:07:59, David Hildenbrand wrote: > On 30.08.19 08:47, Michal Hocko wrote: > > On Fri 30-08-19 08:20:32, David Hildenbrand wrote: > > [...] > >> Regarding shrink_zone_span(), I suspect it was introduced by > >> > >> d0dc12e86b31 ("mm/memory_hotplug: optimize memory hotplug") > >

Re: [PATCH v2 3/6] mm/memory_hotplug: Process all zones when removing memory

2019-08-30 Thread David Hildenbrand
On 30.08.19 08:47, Michal Hocko wrote: > On Fri 30-08-19 08:20:32, David Hildenbrand wrote: > [...] >> Regarding shrink_zone_span(), I suspect it was introduced by >> >> d0dc12e86b31 ("mm/memory_hotplug: optimize memory hotplug") > > zone shrinking code is much older - 815121d2b5cd5. But I do not

Re: [PATCH v2 3/6] mm/memory_hotplug: Process all zones when removing memory

2019-08-30 Thread Michal Hocko
On Fri 30-08-19 08:20:32, David Hildenbrand wrote: [...] > Regarding shrink_zone_span(), I suspect it was introduced by > > d0dc12e86b31 ("mm/memory_hotplug: optimize memory hotplug") zone shrinking code is much older - 815121d2b5cd5. But I do not think this is really needed for Fixes tag. --

Re: [PATCH v2 3/6] mm/memory_hotplug: Process all zones when removing memory

2019-08-30 Thread David Hildenbrand
On 30.08.19 08:01, Michal Hocko wrote: > On Thu 29-08-19 18:59:31, David Hildenbrand wrote: >> On 29.08.19 18:27, Michal Hocko wrote: > [...] >>> No rush, really... It seems this is quite unlikely event as most hotplug >>> usecases simply online memory before removing it later on. >>> >> >> I can

Re: [PATCH v2 3/6] mm/memory_hotplug: Process all zones when removing memory

2019-08-30 Thread Michal Hocko
On Thu 29-08-19 18:59:31, David Hildenbrand wrote: > On 29.08.19 18:27, Michal Hocko wrote: [...] > > No rush, really... It seems this is quite unlikely event as most hotplug > > usecases simply online memory before removing it later on. > > > > I can trigger it reliably right now while

Re: [PATCH v2 3/6] mm/memory_hotplug: Process all zones when removing memory

2019-08-29 Thread David Hildenbrand
On 29.08.19 18:27, Michal Hocko wrote: > On Thu 29-08-19 17:54:35, David Hildenbrand wrote: >> On 29.08.19 17:39, Michal Hocko wrote: >>> On Mon 26-08-19 12:10:09, David Hildenbrand wrote: It is easier than I though to trigger a kernel bug by removing memory that was never onlined. With

Re: [PATCH v2 3/6] mm/memory_hotplug: Process all zones when removing memory

2019-08-29 Thread Michal Hocko
On Thu 29-08-19 17:54:35, David Hildenbrand wrote: > On 29.08.19 17:39, Michal Hocko wrote: > > On Mon 26-08-19 12:10:09, David Hildenbrand wrote: > >> It is easier than I though to trigger a kernel bug by removing memory that > >> was never onlined. With CONFIG_DEBUG_VM the memmap is initialized

Re: [PATCH v2 3/6] mm/memory_hotplug: Process all zones when removing memory

2019-08-29 Thread David Hildenbrand
On 29.08.19 17:39, Michal Hocko wrote: > On Mon 26-08-19 12:10:09, David Hildenbrand wrote: >> It is easier than I though to trigger a kernel bug by removing memory that >> was never onlined. With CONFIG_DEBUG_VM the memmap is initialized with >> garbage, resulting in the detection of a broken

Re: [PATCH v2 3/6] mm/memory_hotplug: Process all zones when removing memory

2019-08-29 Thread Michal Hocko
On Mon 26-08-19 12:10:09, David Hildenbrand wrote: > It is easier than I though to trigger a kernel bug by removing memory that > was never onlined. With CONFIG_DEBUG_VM the memmap is initialized with > garbage, resulting in the detection of a broken zone when removing memory. > Without

[PATCH v2 3/6] mm/memory_hotplug: Process all zones when removing memory

2019-08-26 Thread David Hildenbrand
It is easier than I though to trigger a kernel bug by removing memory that was never onlined. With CONFIG_DEBUG_VM the memmap is initialized with garbage, resulting in the detection of a broken zone when removing memory. Without CONFIG_DEBUG_VM it is less likely - but we could still have garbage