On Tue, Sep 11, 2018 at 5:51 PM, Alexander Duyck <alexander.duyck@xxxxxxxxx> wrote: > 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. You wouldn't need to export it, just make it public to mm/ in mm/internal.h, or a similar local header. With kernel/memremap.c moved to mm/memremap.c this becomes even easier and better scoped for the shared symbols.
