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Wed, 05 May 2021 11:44:24 -0700 (PDT) MIME-Version: 1.0 References: <20210325230938.30752-1-joao.m.martins@oracle.com> <20210325230938.30752-5-joao.m.martins@oracle.com> In-Reply-To: <20210325230938.30752-5-joao.m.martins@oracle.com> From: Dan Williams Date: Wed, 5 May 2021 11:44:29 -0700 Message-ID: Subject: Re: [PATCH v1 04/11] mm/memremap: add ZONE_DEVICE support for compound pages To: Joao Martins Cc: Linux MM , Ira Weiny , linux-nvdimm , Matthew Wilcox , Jason Gunthorpe , Jane Chu , Muchun Song , Mike Kravetz , Andrew Morton Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=intel-com.20150623.gappssmtp.com header.s=20150623 header.b=FP5Wa7op; dmarc=fail reason="No valid SPF, DKIM not aligned (relaxed)" header.from=intel.com (policy=none); spf=none (imf17.hostedemail.com: domain of dan.j.williams@intel.com has no SPF policy when checking 209.85.208.51) smtp.mailfrom=dan.j.williams@intel.com X-Stat-Signature: i39hj3n89x7exxzrrjb3esxkzpirz8sy X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 8327440002E6 Received-SPF: none (intel.com>: No applicable sender policy available) receiver=imf17; identity=mailfrom; envelope-from=""; helo=mail-ed1-f51.google.com; client-ip=209.85.208.51 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620240261-523951 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Mar 25, 2021 at 4:10 PM Joao Martins wrote: > > Add a new align property for struct dev_pagemap which specifies that a > pagemap is composed of a set of compound pages of size @align, instead > of base pages. When these pages are initialised, most are initialised as > tail pages instead of order-0 pages. > > For certain ZONE_DEVICE users like device-dax which have a fixed page > size, this creates an opportunity to optimize GUP and GUP-fast walkers, > treating it the same way as THP or hugetlb pages. > > Signed-off-by: Joao Martins > --- > include/linux/memremap.h | 13 +++++++++++++ > mm/memremap.c | 8 ++++++-- > mm/page_alloc.c | 24 +++++++++++++++++++++++- > 3 files changed, 42 insertions(+), 3 deletions(-) > > diff --git a/include/linux/memremap.h b/include/linux/memremap.h > index b46f63dcaed3..bb28d82dda5e 100644 > --- a/include/linux/memremap.h > +++ b/include/linux/memremap.h > @@ -114,6 +114,7 @@ struct dev_pagemap { > struct completion done; > enum memory_type type; > unsigned int flags; > + unsigned long align; I think this wants some kernel-doc above to indicate that non-zero means "use compound pages with tail-page dedup" and zero / PAGE_SIZE means "use non-compound base pages". The non-zero value must be PAGE_SIZE, PMD_PAGE_SIZE or PUD_PAGE_SIZE. Hmm, maybe it should be an enum: enum devmap_geometry { DEVMAP_PTE, DEVMAP_PMD, DEVMAP_PUD, } ...because it's more than just an alignment it's a structural definition of how the memmap is laid out. > const struct dev_pagemap_ops *ops; > void *owner; > int nr_range; > @@ -130,6 +131,18 @@ static inline struct vmem_altmap *pgmap_altmap(struct dev_pagemap *pgmap) > return NULL; > } > > +static inline unsigned long pgmap_align(struct dev_pagemap *pgmap) > +{ > + if (!pgmap || !pgmap->align) > + return PAGE_SIZE; > + return pgmap->align; > +} > + > +static inline unsigned long pgmap_pfn_align(struct dev_pagemap *pgmap) > +{ > + return PHYS_PFN(pgmap_align(pgmap)); > +} > + > #ifdef CONFIG_ZONE_DEVICE > bool pfn_zone_device_reserved(unsigned long pfn); > void *memremap_pages(struct dev_pagemap *pgmap, int nid); > diff --git a/mm/memremap.c b/mm/memremap.c > index 805d761740c4..d160853670c4 100644 > --- a/mm/memremap.c > +++ b/mm/memremap.c > @@ -318,8 +318,12 @@ static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params, > memmap_init_zone_device(&NODE_DATA(nid)->node_zones[ZONE_DEVICE], > PHYS_PFN(range->start), > PHYS_PFN(range_len(range)), pgmap); > - percpu_ref_get_many(pgmap->ref, pfn_end(pgmap, range_id) > - - pfn_first(pgmap, range_id)); > + if (pgmap_align(pgmap) > PAGE_SIZE) > + percpu_ref_get_many(pgmap->ref, (pfn_end(pgmap, range_id) > + - pfn_first(pgmap, range_id)) / pgmap_pfn_align(pgmap)); > + else > + percpu_ref_get_many(pgmap->ref, pfn_end(pgmap, range_id) > + - pfn_first(pgmap, range_id)); > return 0; > > err_add_memory: > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 58974067bbd4..3a77f9e43f3a 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -6285,6 +6285,8 @@ void __ref memmap_init_zone_device(struct zone *zone, > unsigned long pfn, end_pfn = start_pfn + nr_pages; > struct pglist_data *pgdat = zone->zone_pgdat; > struct vmem_altmap *altmap = pgmap_altmap(pgmap); > + unsigned int pfn_align = pgmap_pfn_align(pgmap); > + unsigned int order_align = order_base_2(pfn_align); > unsigned long zone_idx = zone_idx(zone); > unsigned long start = jiffies; > int nid = pgdat->node_id; > @@ -6302,10 +6304,30 @@ void __ref memmap_init_zone_device(struct zone *zone, > nr_pages = end_pfn - start_pfn; > } > > - for (pfn = start_pfn; pfn < end_pfn; pfn++) { > + for (pfn = start_pfn; pfn < end_pfn; pfn += pfn_align) { pfn_align is in bytes and pfn is in pages... is there a "pfn_align >>= PAGE_SHIFT" I missed somewhere?