Wei Xu <weixugc@xxxxxxxxxx> writes: > 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. Sounds good to me! Thanks! Will change this in the next version. Best Regards, Huang, Ying >> + 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 >>
