From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH 2/3] mm: add find_alloc_contig_pages() interface Date: Sun, 22 Apr 2018 18:09:43 -0600 Message-ID: <20180423000943.GO17484@dhcp22.suse.cz> References: <20180417020915.11786-1-mike.kravetz@oracle.com> <20180417020915.11786-3-mike.kravetz@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20180417020915.11786-3-mike.kravetz@oracle.com> Sender: linux-kernel-owner@vger.kernel.org To: Mike Kravetz Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Reinette Chatre , Christopher Lameter , Guy Shattah , Anshuman Khandual , Michal Nazarewicz , Vlastimil Babka , David Nellans , Laura Abbott , Pavel Machek , Dave Hansen , Andrew Morton List-Id: linux-api@vger.kernel.org On Mon 16-04-18 19:09:14, Mike Kravetz wrote: [...] > @@ -2010,9 +2011,13 @@ static __always_inline struct page *__rmqueue_cma_fallback(struct zone *zone, > { > return __rmqueue_smallest(zone, order, MIGRATE_CMA); > } > +#define contig_alloc_migratetype_ok(migratetype) \ > + ((migratetype) == MIGRATE_CMA || (migratetype) == MIGRATE_MOVABLE) > #else > static inline struct page *__rmqueue_cma_fallback(struct zone *zone, > unsigned int order) { return NULL; } > +#define contig_alloc_migratetype_ok(migratetype) \ > + ((migratetype) == MIGRATE_MOVABLE) > #endif > > /* > @@ -7822,6 +7827,9 @@ int alloc_contig_range(unsigned long start, unsigned long end, > }; > INIT_LIST_HEAD(&cc.migratepages); > > + if (!contig_alloc_migratetype_ok(migratetype)) > + return -EINVAL; > + > > /* > * What we do here is we mark all pageblocks in range as > * MIGRATE_ISOLATE. Because pageblock and max order pages may > @@ -7912,8 +7920,9 @@ int alloc_contig_range(unsigned long start, unsigned long end, > > /* Make sure the range is really isolated. */ > if (test_pages_isolated(outer_start, end, false)) { > - pr_info_ratelimited("%s: [%lx, %lx) PFNs busy\n", > - __func__, outer_start, end); > + if (!(migratetype == MIGRATE_MOVABLE)) /* only print for CMA */ > + pr_info_ratelimited("%s: [%lx, %lx) PFNs busy\n", > + __func__, outer_start, end); > ret = -EBUSY; > goto done; > } This probably belongs to a separate patch. I would be tempted to say that we should get rid of this migratetype thingy altogether. I confess I have forgot everything about why this is required actually but it is ugly as hell. Not your fault of course. > @@ -7949,6 +7958,82 @@ void free_contig_range(unsigned long pfn, unsigned long nr_pages) > } > WARN(count != 0, "%ld pages are still in use!\n", count); > } > + > +static bool contig_pfn_range_valid(struct zone *z, unsigned long start_pfn, > + unsigned long nr_pages) > +{ > + unsigned long i, end_pfn = start_pfn + nr_pages; > + struct page *page; > + > + for (i = start_pfn; i < end_pfn; i++) { > + if (!pfn_valid(i)) > + return false; > + > + page = pfn_to_page(i); It believe we want pfn_to_online_page here. The old giga pages code is buggy in that regard but nothing really critical because the alloc_contig_range will notice that. Also do we want to check other usual suspects? E.g. PageReserved? And generally migrateable pages if page count > 0. Or do we want to leave everything to the alloc_contig_range? > + > + if (page_zone(page) != z) > + return false; > + > + } > + > + return true; > +} > + > +/** > + * find_alloc_contig_pages() -- attempt to find and allocate a contiguous > + * range of pages > + * @order: number of pages > + * @gfp: gfp mask used to limit search as well as during compaction > + * @nid: target node > + * @nodemask: mask of other possible nodes > + * > + * Pages can be freed with a call to free_contig_pages(), or by manually > + * calling __free_page() for each page allocated. > + * > + * Return: pointer to 'order' pages on success, or NULL if not successful. > + */ > +struct page *find_alloc_contig_pages(unsigned int order, gfp_t gfp, > + int nid, nodemask_t *nodemask) Vlastimil asked about this but I would even say that we do not want to make this order based. Why would we want to restrict the api to 2^order sizes in the first place? What if somebody wants to allocate 123 pages? > +{ > + unsigned long pfn, nr_pages, flags; > + struct page *ret_page = NULL; > + struct zonelist *zonelist; > + struct zoneref *z; > + struct zone *zone; > + int rc; > + > + nr_pages = 1 << order; > + zonelist = node_zonelist(nid, gfp); > + for_each_zone_zonelist_nodemask(zone, z, zonelist, gfp_zone(gfp), > + nodemask) { > + spin_lock_irqsave(&zone->lock, flags); > + pfn = ALIGN(zone->zone_start_pfn, nr_pages); > + while (zone_spans_pfn(zone, pfn + nr_pages - 1)) { > + if (contig_pfn_range_valid(zone, pfn, nr_pages)) { > + spin_unlock_irqrestore(&zone->lock, flags); I know that the giga page allocation does use the zone lock but why? I suspect it wants to stabilize zone_start_pfn but zone lock doesn't do that. > + > + rc = alloc_contig_range(pfn, pfn + nr_pages, > + MIGRATE_MOVABLE, gfp); > + if (!rc) { > + ret_page = pfn_to_page(pfn); > + return ret_page; > + } > + spin_lock_irqsave(&zone->lock, flags); > + } > + pfn += nr_pages; > + } > + spin_unlock_irqrestore(&zone->lock, flags); > + } Other than that this API looks much saner than alloc_contig_range. We still need to sort out some details (e.g. alignment) but it should be an improvement. Thanks! -- Michal Hocko SUSE Labs