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charset=UTF-8 X-Rspam-User: X-Stat-Signature: 7bmbbct54wbi636uz4ygwcfdop1rpe6r X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: BC90F1C000C X-HE-Tag: 1782896917-671229 X-HE-Meta: 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 6l/C6YU3 hnHHYO6Gx4o9zDfzXih/UXUUbMRBbE9SXqDWHBDcXakgQKUGUMK4VFu1FfWhcAOfm2AEbclE/bGlZsYyqMZvdS7FoqhYKMeAgkhwbCe0OmrTcmEPJQNSlGVf/iW+BjsNR3bNfCXkQDx+9AWcywuv/YzcECoQ1m6otzhZpzNVUmP9aiK0izwjddAER8Sk7wFXP05qshKOYh04J49RzC2Xy1MElgTt7C4J1tufFnS+AiFluYA3L/cu7gji6Zev3O+ICbPci Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. The optimized path assigns _refcount through the copied template, so keep it disabled when the page_ref_set tracepoint is enabled. This patch accelerates head-page initialization. The pfns_per_compound == 1 case gets the full benefit here, compound tails are handled in the next patch. Tested in a VM with a 100 GB fsdax namespace device configured with map=dev on Intel Ice Lake server. This test exercises the nd_pmem rebind path (pfns_per_compound == 1). Test procedure: Rebind the nd_pmem driver 30 times and collect the memmap initialization time from the pr_debug() output of memmap_init_zone_device(). Base(v7.2-rc1): First binding: 1456 ms Average of subsequent rebinds: 244.28 ms With this patch and its prerequisites applied: First binding: 1440 ms Average of subsequent rebinds: 217.19 ms This reduces the average rebind time from 244.28 ms to 217.19 ms, or about 11%. Signed-off-by: Li Zhe --- 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)); +} + /* * With compound page geometry and when struct pages are stored in ram most * tail pages are reused. Consequently, the amount of unique struct pages to @@ -1121,6 +1165,7 @@ void __ref memmap_init_zone_device(struct zone *zone, unsigned long nr_pages, struct dev_pagemap *pgmap) { + bool use_template = zone_device_page_init_optimization_enabled(); unsigned long pfn, end_pfn = start_pfn + nr_pages; struct pglist_data *pgdat = zone->zone_pgdat; struct vmem_altmap *altmap = pgmap_altmap(pgmap); @@ -1128,6 +1173,7 @@ void __ref memmap_init_zone_device(struct zone *zone, unsigned long zone_idx = zone_idx(zone); unsigned long start = jiffies; int nid = pgdat->node_id; + struct page template; if (WARN_ON_ONCE(!pgmap || zone_idx != ZONE_DEVICE)) return; @@ -1142,10 +1188,36 @@ void __ref memmap_init_zone_device(struct zone *zone, nr_pages = end_pfn - start_pfn; } - for (pfn = start_pfn; pfn < end_pfn; pfn += pfns_per_compound) { - struct page *page = pfn_to_page(pfn); + + if (!nr_pages) + return; + + pfn = start_pfn; + /* + * Seed the reusable head-page template from the first real struct + * page, because the existing page-init and pageblock helpers expect + * a real memmap entry rather than a stack object. + */ + if (use_template) { + struct page *page = pfn_to_page(start_pfn); zone_device_page_init_slow(page, pfn, zone_idx, nid, pgmap); + zone_device_template_page_init(&template, page); + if (pfns_per_compound != 1) + memmap_init_compound(page, pfn, zone_idx, nid, pgmap, + compound_nr_pages(start_pfn, altmap, pgmap)); + pfn += pfns_per_compound; + } + + for (; pfn < end_pfn; pfn += pfns_per_compound) { + struct page *page = pfn_to_page(pfn); + + if (use_template) + zone_device_page_init_from_template(page, pfn, + &template); + else + zone_device_page_init_slow(page, pfn, zone_idx, + nid, pgmap); if (IS_ALIGNED(pfn, PAGES_PER_SECTION)) cond_resched(); -- 2.20.1