On Fri, Jun 25, 2021 at 12:33 AM Huang Ying <ying.huang@xxxxxxxxx> wrote: > > From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > > This is mostly derived from a patch from Yang Shi: > > https://lore.kernel.org/linux-mm/1560468577-101178-10-git-send-email-yang.shi@xxxxxxxxxxxxxxxxx/ > > Add code to the reclaim path (shrink_page_list()) to "demote" data > to another NUMA node instead of discarding the data. This always > avoids the cost of I/O needed to read the page back in and sometimes > avoids the writeout cost when the page is dirty. > > A second pass through shrink_page_list() will be made if any demotions > fail. This essentially falls back to normal reclaim behavior in the > case that demotions fail. Previous versions of this patch may have > simply failed to reclaim pages which were eligible for demotion but > were unable to be demoted in practice. > > For some cases, for example, MADV_PAGEOUT, the pages are always > discarded instead of demoted to follow the kernel API definition. > Because MADV_PAGEOUT is defined as freeing specified pages regardless > in which tier they are. > > Note: This just adds the start of infrastructure for migration. It is > actually disabled next to the FIXME in migrate_demote_page_ok(). > > Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> > Reviewed-by: Yang Shi <shy828301@xxxxxxxxx> > Reviewed-by: Wei Xu <weixugc@xxxxxxxxxx> > Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxx> > Cc: Zi Yan <ziy@xxxxxxxxxx> > Cc: David Rientjes <rientjes@xxxxxxxxxx> > Cc: Dan Williams <dan.j.williams@xxxxxxxxx> > > -- > changes from 20210618: > * Fix some typos in comments and patch description. > * Fix MADV_PAGEOUT behavior per Zi's comments. > > changes from 20210122: > * move from GFP_HIGHUSER -> GFP_HIGHUSER_MOVABLE (Ying) > > changes from 202010: > * add MR_NUMA_MISPLACED to trace MIGRATE_REASON define > * make migrate_demote_page_ok() static, remove 'sc' arg until > later patch > * remove unnecessary alloc_demote_page() hugetlb warning > * Simplify alloc_demote_page() gfp mask. Depend on > __GFP_NORETRY to make it lightweight instead of fancier > stuff like leaving out __GFP_IO/FS. > * Allocate migration page with alloc_migration_target() > instead of allocating directly. > changes from 20200730: > * Add another pass through shrink_page_list() when demotion > fails. > changes from 20210302: > * Use __GFP_THISNODE and revise the comment explaining the > GFP mask constructionn > --- > include/linux/migrate.h | 9 ++++ > include/trace/events/migrate.h | 3 +- > mm/vmscan.c | 93 ++++++++++++++++++++++++++++++++++ > 3 files changed, 104 insertions(+), 1 deletion(-) > > diff --git a/include/linux/migrate.h b/include/linux/migrate.h > index 166dc1fe4eee..d678e02a27ff 100644 > --- a/include/linux/migrate.h > +++ b/include/linux/migrate.h > @@ -28,6 +28,7 @@ enum migrate_reason { > MR_NUMA_MISPLACED, > MR_CONTIG_RANGE, > MR_LONGTERM_PIN, > + MR_DEMOTION, > MR_TYPES > }; > > @@ -191,6 +192,14 @@ struct migrate_vma { > int migrate_vma_setup(struct migrate_vma *args); > void migrate_vma_pages(struct migrate_vma *migrate); > void migrate_vma_finalize(struct migrate_vma *migrate); > +int next_demotion_node(int node); > + > +#else /* CONFIG_MIGRATION disabled: */ > + > +static inline int next_demotion_node(int node) > +{ > + return NUMA_NO_NODE; > +} > > #endif /* CONFIG_MIGRATION */ > > diff --git a/include/trace/events/migrate.h b/include/trace/events/migrate.h > index 9fb2a3bbcdfb..779f3fad9ecd 100644 > --- a/include/trace/events/migrate.h > +++ b/include/trace/events/migrate.h > @@ -21,7 +21,8 @@ > EM( MR_MEMPOLICY_MBIND, "mempolicy_mbind") \ > EM( MR_NUMA_MISPLACED, "numa_misplaced") \ > EM( MR_CONTIG_RANGE, "contig_range") \ > - EMe(MR_LONGTERM_PIN, "longterm_pin") > + EM( MR_LONGTERM_PIN, "longterm_pin") \ > + EMe(MR_DEMOTION, "demotion") > > /* > * First define the enums in the above macros to be exported to userspace > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 5199b9696bab..badaf3d4360d 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -41,6 +41,7 @@ > #include <linux/kthread.h> > #include <linux/freezer.h> > #include <linux/memcontrol.h> > +#include <linux/migrate.h> > #include <linux/delayacct.h> > #include <linux/sysctl.h> > #include <linux/oom.h> > @@ -118,6 +119,9 @@ struct scan_control { > /* The file pages on the current node are dangerously low */ > unsigned int file_is_tiny:1; > > + /* Always discard instead of demoting to lower tier memory */ > + unsigned int no_demotion:1; > + > /* Allocation order */ > s8 order; > > @@ -1231,6 +1235,27 @@ static enum page_references page_check_references(struct page *page, > return PAGEREF_RECLAIM; > } > > +static bool migrate_demote_page_ok(struct page *page, > + struct scan_control *sc) > +{ > + int next_nid; > + > + VM_BUG_ON_PAGE(!PageLocked(page), page); > + VM_BUG_ON_PAGE(PageHuge(page), page); > + VM_BUG_ON_PAGE(PageLRU(page), page); > + > + if (sc->no_demotion) > + return false; > + next_nid = next_demotion_node(page_to_nid(page)); > + if (next_nid == NUMA_NO_NODE) > + return false; The above sc and node checks are not specific to the page. They can be moved into shrink_page_list() to set do_demote_pass accordingly. We then don't need to repeat these checks for every page. > + if (PageTransHuge(page) && !thp_migration_supported()) > + return false; > + > + // FIXME: actually enable this later in the series > + return false; > +} > + > /* Check if a page is dirty or under writeback */ > static void page_check_dirty_writeback(struct page *page, > bool *dirty, bool *writeback) > @@ -1261,6 +1286,49 @@ static void page_check_dirty_writeback(struct page *page, > mapping->a_ops->is_dirty_writeback(page, dirty, writeback); > } > > +static struct page *alloc_demote_page(struct page *page, unsigned long node) > +{ > + struct migration_target_control mtc = { > + /* > + * Allocate from 'node', or fail quickly and quietly. > + * When this happens, 'page' will likely just be discarded > + * instead of migrated. > + */ > + .gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | > + __GFP_THISNODE | __GFP_NOWARN | > + __GFP_NOMEMALLOC | GFP_NOWAIT, > + .nid = node > + }; > + > + return alloc_migration_target(page, (unsigned long)&mtc); > +} > + > +/* > + * Take pages on @demote_list and attempt to demote them to > + * another node. Pages which are not demoted are left on > + * @demote_pages. > + */ > +static unsigned int demote_page_list(struct list_head *demote_pages, > + struct pglist_data *pgdat) > +{ > + int target_nid = next_demotion_node(pgdat->node_id); > + unsigned int nr_succeeded; > + int err; > + > + if (list_empty(demote_pages)) > + return 0; > + > + if (target_nid == NUMA_NO_NODE) > + return 0; > + > + /* Demotion ignores all cpuset and mempolicy settings */ > + err = migrate_pages(demote_pages, alloc_demote_page, NULL, > + target_nid, MIGRATE_ASYNC, MR_DEMOTION, > + &nr_succeeded); > + > + return nr_succeeded; > +} > + > /* > * shrink_page_list() returns the number of reclaimed pages > */ > @@ -1272,12 +1340,15 @@ static unsigned int shrink_page_list(struct list_head *page_list, > { > LIST_HEAD(ret_pages); > LIST_HEAD(free_pages); > + LIST_HEAD(demote_pages); > unsigned int nr_reclaimed = 0; > unsigned int pgactivate = 0; > + bool do_demote_pass = true; > > memset(stat, 0, sizeof(*stat)); > cond_resched(); > > +retry: > while (!list_empty(page_list)) { > struct address_space *mapping; > struct page *page; > @@ -1426,6 +1497,16 @@ static unsigned int shrink_page_list(struct list_head *page_list, > ; /* try to reclaim the page below */ > } > > + /* > + * Before reclaiming the page, try to relocate > + * its contents to another node. > + */ > + if (do_demote_pass && migrate_demote_page_ok(page, sc)) { > + list_add(&page->lru, &demote_pages); > + unlock_page(page); > + continue; > + } > + > /* > * Anonymous process memory has backing store? > * Try to allocate it some swap space here. > @@ -1676,6 +1757,17 @@ static unsigned int shrink_page_list(struct list_head *page_list, > list_add(&page->lru, &ret_pages); > VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page); > } > + /* 'page_list' is always empty here */ > + > + /* Migrate pages selected for demotion */ > + nr_reclaimed += demote_page_list(&demote_pages, pgdat); > + /* Pages that could not be demoted are still in @demote_pages */ > + if (!list_empty(&demote_pages)) { > + /* Pages which failed to demoted go back on @page_list for retry: */ > + list_splice_init(&demote_pages, page_list); > + do_demote_pass = false; > + goto retry; > + } > > pgactivate = stat->nr_activate[0] + stat->nr_activate[1]; > > @@ -2312,6 +2404,7 @@ unsigned long reclaim_pages(struct list_head *page_list) > .may_writepage = 1, > .may_unmap = 1, > .may_swap = 1, > + .no_demotion = 1, > }; > > while (!list_empty(page_list)) { > -- > 2.30.2 >
