On Fri, 3 Jul 2026 17:06:33 +0300, [email protected] wrote: > On Wed, Jul 01, 2026 at 05:05:49PM +0800, Li Zhe wrote: > > memmap_init_zone_device() repeats nearly identical head-page > > initialization for each PFN. Prepare one reusable ZONE_DEVICE head-page > > template through the existing slow path, refresh the PFN-dependent > > fields in that template before each copy, and memcpy it into each > > destination page. > > > > This reduces the average rebind time from 244.28 ms to 217.19 ms, or > > about 11%. > > > > Signed-off-by: Li Zhe <[email protected]> > > --- > > mm/mm_init.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++-- > > 1 file changed, 74 insertions(+), 2 deletions(-) > > > > diff --git a/mm/mm_init.c b/mm/mm_init.c > > index 4c7fad440c2a..cc8417951467 100644 > > --- a/mm/mm_init.c > > +++ b/mm/mm_init.c > > @@ -1066,6 +1066,50 @@ static void __ref zone_device_page_init_slow(struct > > page *page, > > set_page_count(page, 0); > > } > > > > +static inline bool zone_device_page_init_optimization_enabled(void) > > +{ > > + /* > > + * The template fast path copies a preinitialized struct page image. > > + * Skip it when the page_ref_set tracepoint is enabled. > > + */ > > + return !page_ref_tracepoint_active(page_ref_set); > > +} > > + > > +static inline void zone_device_template_page_init(struct page *template, > > + struct page *src) > > +{ > > + memcpy(template, src, sizeof(*template)); > > +} > > + > > +/* > > + * 'template' is a reusable page prototype rather than a strictly immutable > > + * object. Most ZONE_DEVICE fields stay constant across the pages covered > > by > > + * the current template, but section bits and page->virtual may still > > depend > > + * on the PFN. Refresh those PFN-dependent fields in the template before > > + * copying it into @page. > > + */ > > +static inline void zone_device_page_update_template(struct page *template, > > + unsigned long pfn) > > +{ > > + set_page_section_from_pfn(template, pfn); > > +#ifdef WANT_PAGE_VIRTUAL > > + if (!is_highmem_idx(ZONE_DEVICE)) > > + set_page_address(template, __va(pfn << PAGE_SHIFT)); > > +#endif > > +} > > + > > +static void zone_device_page_init_from_template(struct page *page, > > + unsigned long pfn, struct page *template) > > +{ > > + /* > > + * 'template' carries the invariant portion of a ZONE_DEVICE struct > > + * page. Update the PFN-dependent fields in place before copying it > > + * to the destination page. > > + */ > > + zone_device_page_update_template(template, pfn); > > + memcpy(page, template, sizeof(*page)); > > +} > > + > > The whole bunch of template functions look like it could be useful for > initialization of the non-zone-device struct pages as well. > > As I mentioned previously, it's interesting to see if this approach speeds > up normal memory map initialization as well. If if does could have a single > set of the template functions.
Thanks for the suggestion. I agree this is worth exploring. For this series, I would prefer to keep the scope limited to the ZONE_DEVICE initialization path and get that part settled first. After this series is settled, I plan to look into whether a similar template-based approach can also help normal page initialization. If it shows a real benefit there as well, I can follow up with a separate series. Thanks, Zhe
