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. -- Sincerely yours, Mike.
