On Tue, Sep 11, 2018 at 3:35 PM Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > > On Mon, Sep 10, 2018 at 4:43 PM, Alexander Duyck > <alexander.duyck@xxxxxxxxx> wrote: > > > > From: Alexander Duyck <alexander.h.duyck@xxxxxxxxx> > > > > 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 > > drivers. > > > > Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxx> > > --- > > include/linux/mm.h | 2 + > > kernel/memremap.c | 24 +++++--------- > > mm/hmm.c | 12 ++++--- > > mm/page_alloc.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++- > > Hmm, why mm/page_alloc.c and not kernel/memremap.c for this new > helper? I think that would address the kbuild reports and keeps all > the devm_memremap_pages / ZONE_DEVICE special casing centralized. I > also think it makes sense to move memremap.c to mm/ rather than > kernel/ especially since commit 5981690ddb8f "memremap: split > devm_memremap_pages() and memremap() infrastructure". Arguably, that > commit should have went ahead with the directory move. The issue ends up being the fact that I would then have to start exporting infrastructure such as __init_single_page from page_alloc. I have some follow-up patches I am working on that will generate some other shared functions that can be used by both memmap_init_zone and memmap_init_zone_device, as well as pulling in some of the code from the deferred memory init.
