On Tue, Sep 25, 2018 at 1:29 PM Alexander Duyck
The ZONE_DEVICE pages were being initialized in two locations. One was with
the memory_hotplug lock held and another was outside of that lock. The
problem with this is that it was nearly doubling the memory initialization
time. Instead of doing this twice, once while holding a global lock and
once without, I am opting to defer the initialization to the one outside of
the lock. This allows us to avoid serializing the overhead for memory init
and we can instead focus on per-node init times.
One issue I encountered is that devm_memremap_pages and
hmm_devmmem_pages_create were initializing only the pgmap field the same
way. One wasn't initializing hmm_data, and the other was initializing it to
a poison value. Since this is something that is exposed to the driver in
the case of hmm I am opting for a third option and just initializing
hmm_data to 0 since this is going to be exposed to unknown third party
Reviewed-by: Pavel Tatashin <pavel.tatashin(a)microsoft.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck(a)linux.intel.com>
v4: Moved moved memmap_init_zone_device to below memmmap_init_zone to avoid
merge conflicts with other changes in the kernel.
v5: No change
This patch appears to cause a regression in the "create.sh" unit test
in the ndctl test suite.
I tried to reproduce on -next with:
2302f5ee215e mm: defer ZONE_DEVICE page initialization to the point
where we init pgmap
...but -next does not even boot for me at that commit.
Here is a warning signature that proceeds a hang with this patch
applied against v4.19-rc6:
percpu ref (blk_queue_usage_counter_release) <= 0 (-1530626) after
switching to atomic
WARNING: CPU: 24 PID: 7346 at lib/percpu-refcount.c:155
CPU: 24 PID: 7346 Comm: modprobe Tainted: G OE 4.19.0-rc6+ #2458