From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f44.google.com (mail-pj1-f44.google.com [209.85.216.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B47EC168 for ; Thu, 15 Jul 2021 01:08:25 +0000 (UTC) Received: by mail-pj1-f44.google.com with SMTP id i16-20020a17090acf90b02901736d9d2218so2930206pju.1 for ; Wed, 14 Jul 2021 18:08:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=NN59F4vDIomsgEBtl8RXR+we5E2TKHGqeWPAOiMz83k=; b=ebWDJrPYcGhCMLRRnJefgXT043Kg8pFLEAtlL3VyJQiDiZuQH3KQFfdprQeMEabNar UjePn/JW7BVX+VHqq1f27aRC8x+jwZ4crlPjawlupdFEgvsQ/DHPfzbwBSF2aZ8JDbXL 2j80xem3naLZ6+voKnmlWBi6wyVAuHp5lXxgpQ/nquuUr6bU/oYokMNyPB6vD01ZDvjE z4jtZbWC+NM0+HVC1eTdLJBu9CeRNHJZ8Tc7oTENW4cQYeO4G/+NrbUybGkxggjaEvU+ dksLg470Niwmd+16f1F6FSO6fV6xwPqzT2uSgVmtfF0T53LSybyC7vidRzKAFL6lyviW 0cIA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=NN59F4vDIomsgEBtl8RXR+we5E2TKHGqeWPAOiMz83k=; b=rOIYDwc4PM+DAU62rp+KHgGOX45M7zQQ2VMN1EB8fKd3az+yaYE8HfY6o9OoepJCHt XVJ/QtI56B46fURnFTel6BdjB9mdNKlVvtQ+0FRkMhcJpzOfdGPRod4XwCGWr3tXmNyH HXB6ekx8FqyuYPsTObNL2rKbZouZ+qfDUzuUBoBKt5w5oOszsAc+R99wmwUzJK3pDIfj xiKD0Fvn32nwruD/7OkROJSLIbCU49Y7zv+lxEChiky6AMQmghGBZh6qETWsI9V2/lho tYLhD3eYRUlP4/OkIKouqdkPxY5J/kvIki2ez/i+zU4F0O2/7qTFhcXCNmiUsOjgxaGP xJfg== X-Gm-Message-State: AOAM531h17o0Q4Qh+A5IuyxBO8UB+WJeJu6fBwd9I0cRWXUp2QK6yAy+ qrtI0Ala8v9sxPQBrkmsXxcTJxJs3oT1FOO9qbRSlw== X-Google-Smtp-Source: ABdhPJwtcooUH/eYMB5vJXqE/PQhaN/7W0oePw41gDnxWZv+L/ZaInmAjJON0D+NGCN2uutz7j4LgWuQlh82L9fw7cA= X-Received: by 2002:a17:90a:8407:: with SMTP id j7mr6550677pjn.13.1626311305135; Wed, 14 Jul 2021 18:08:25 -0700 (PDT) Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20210714193542.21857-1-joao.m.martins@oracle.com> <20210714193542.21857-5-joao.m.martins@oracle.com> In-Reply-To: <20210714193542.21857-5-joao.m.martins@oracle.com> From: Dan Williams Date: Wed, 14 Jul 2021 18:08:14 -0700 Message-ID: Subject: Re: [PATCH v3 04/14] mm/memremap: add ZONE_DEVICE support for compound pages To: Joao Martins Cc: Linux MM , Vishal Verma , Dave Jiang , Naoya Horiguchi , Matthew Wilcox , Jason Gunthorpe , John Hubbard , Jane Chu , Muchun Song , Mike Kravetz , Andrew Morton , Jonathan Corbet , Linux NVDIMM , Linux Doc Mailing List Content-Type: text/plain; charset="UTF-8" On Wed, Jul 14, 2021 at 12:36 PM Joao Martins wrote: > > Add a new align property for struct dev_pagemap which specifies that a s/align/@geometry/ > pagemap is composed of a set of compound pages of size @align, s/@align/@geometry/ > instead of > base pages. When a compound page geometry is requested, all but the first > page 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 | 17 +++++++++++++++++ > mm/memremap.c | 8 ++++++-- > mm/page_alloc.c | 34 +++++++++++++++++++++++++++++++++- > 3 files changed, 56 insertions(+), 3 deletions(-) > > diff --git a/include/linux/memremap.h b/include/linux/memremap.h > index 119f130ef8f1..e5ab6d4525c1 100644 > --- a/include/linux/memremap.h > +++ b/include/linux/memremap.h > @@ -99,6 +99,10 @@ struct dev_pagemap_ops { > * @done: completion for @internal_ref > * @type: memory type: see MEMORY_* in memory_hotplug.h > * @flags: PGMAP_* flags to specify defailed behavior > + * @geometry: structural definition of how the vmemmap metadata is populated. > + * A zero or PAGE_SIZE defaults to using base pages as the memmap metadata > + * representation. A bigger value but also multiple of PAGE_SIZE will set > + * up compound struct pages representative of the requested geometry size. > * @ops: method table > * @owner: an opaque pointer identifying the entity that manages this > * instance. Used by various helpers to make sure that no > @@ -114,6 +118,7 @@ struct dev_pagemap { > struct completion done; > enum memory_type type; > unsigned int flags; > + unsigned long geometry; > const struct dev_pagemap_ops *ops; > void *owner; > int nr_range; > @@ -130,6 +135,18 @@ static inline struct vmem_altmap *pgmap_altmap(struct dev_pagemap *pgmap) > return NULL; > } > > +static inline unsigned long pgmap_geometry(struct dev_pagemap *pgmap) > +{ > + if (!pgmap || !pgmap->geometry) > + return PAGE_SIZE; > + return pgmap->geometry; > +} > + > +static inline unsigned long pgmap_pfn_geometry(struct dev_pagemap *pgmap) > +{ > + return PHYS_PFN(pgmap_geometry(pgmap)); > +} Are both needed? Maybe just have ->geometry natively be in nr_pages units directly, because pgmap_pfn_geometry() makes it confusing whether it's a geometry of the pfn or the geometry of the 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..ffcb924eb6a5 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_geometry(pgmap) > PAGE_SIZE) This would become if (pgmap_geometry(pgmap) > 1) > + percpu_ref_get_many(pgmap->ref, (pfn_end(pgmap, range_id) > + - pfn_first(pgmap, range_id)) / pgmap_pfn_geometry(pgmap)); ...and this would be pgmap_geometry() > + 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 79f3b38afeca..188cb5f8c308 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -6597,6 +6597,31 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn, > } > } > > +static void __ref memmap_init_compound(struct page *page, unsigned long pfn, I'd feel better if @page was renamed @head... more below: > + unsigned long zone_idx, int nid, > + struct dev_pagemap *pgmap, > + unsigned long nr_pages) > +{ > + unsigned int order_align = order_base_2(nr_pages); > + unsigned long i; > + > + __SetPageHead(page); > + > + for (i = 1; i < nr_pages; i++) { The switch of loop styles is jarring. I.e. the switch from memmap_init_zone_device() that is using pfn, end_pfn, and a local 'struct page *' variable to this helper using pfn + i and a mix of helpers (__init_zone_device_page, prep_compound_tail) that have different expectations of head page + tail_idx and current page. I.e. this reads more obviously correct to me, but maybe I'm just in the wrong headspace: for (pfn = head_pfn + 1; pfn < end_pfn; pfn++) { struct page *page = pfn_to_page(pfn); __init_zone_device_page(page, pfn, zone_idx, nid, pgmap); prep_compound_tail(head, pfn - head_pfn); > + __init_zone_device_page(page + i, pfn + i, zone_idx, > + nid, pgmap); > + prep_compound_tail(page, i); > + > + /* > + * The first and second tail pages need to > + * initialized first, hence the head page is > + * prepared last. I'd change this comment to say why rather than restate what can be gleaned from the code. It's actually not clear to me why this order is necessary. > + */ > + if (i == 2) > + prep_compound_head(page, order_align); > + } > +} > + > void __ref memmap_init_zone_device(struct zone *zone, > unsigned long start_pfn, > unsigned long nr_pages, > @@ -6605,6 +6630,7 @@ 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 pfns_per_compound = pgmap_pfn_geometry(pgmap); > unsigned long zone_idx = zone_idx(zone); > unsigned long start = jiffies; > int nid = pgdat->node_id; > @@ -6622,10 +6648,16 @@ 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 += pfns_per_compound) { > struct page *page = pfn_to_page(pfn); > > __init_zone_device_page(page, pfn, zone_idx, nid, pgmap); > + > + if (pfns_per_compound == 1) > + continue; > + > + memmap_init_compound(page, pfn, zone_idx, nid, pgmap, > + pfns_per_compound); I otherwise don't see anything broken with this patch, so feel free to include: Reviewed-by: Dan Williams ...on the resend with the fixups.