From: Baoquan He Add per-walk counters to measure empty aging walks which traverse an mm's page tables but find no folio for the current lruvec (node+memcg). These are common on multi-NUMA node systems because lru_gen_use_mm() marks an mm for all nodes at every context switch. New counters (accumulated in mm_state->stats[]): MM_LEAF_ASSOCIATED - leaf entries whose folio is in this lruvec MM_WALK_TOTAL - page-table walks completed MM_WALK_EMPTY - walks that found no folio in this lruvec MM_LEAF_EMPTY_WALKS - leaf entries scanned during empty walks A new tracepoint, mm_vmscan_lru_gen_walk(), fires after each walk, and the debugfs lru_gen output ("TYFALWEE") exposes the new counters. Reviewed-by: Barry Song Signed-off-by: Baoquan He Signed-off-by: Baoquan He --- include/linux/mmzone.h | 4 ++++ mm/trace_vmscan.h | 28 ++++++++++++++++++++++++++++ mm/vmscan.c | 32 ++++++++++++++++++++++++++++---- 3 files changed, 60 insertions(+), 4 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index c161d563ce8f..a49efd9b74ed 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -579,6 +579,10 @@ enum { MM_LEAF_YOUNG, /* young leaf entries */ MM_NONLEAF_FOUND, /* non-leaf entries found in Bloom filters */ MM_NONLEAF_ADDED, /* non-leaf entries added to Bloom filters */ + MM_LEAF_ASSOCIATED, /* leaf entries whose folio is in this lruvec (node+memcg) */ + MM_WALK_TOTAL, /* page-table walks completed */ + MM_WALK_EMPTY, /* walks that found no folio in this lruvec */ + MM_LEAF_EMPTY_WALKS, /* leaf entries scanned during empty walks */ NR_MM_STATS }; diff --git a/mm/trace_vmscan.h b/mm/trace_vmscan.h index 565c56428364..4884fc7a35b9 100644 --- a/mm/trace_vmscan.h +++ b/mm/trace_vmscan.h @@ -763,6 +763,34 @@ TRACE_EVENT(mm_vmscan_kswapd_clear_hopeless, __entry->nid, __print_symbolic(__entry->reason, kswapd_clear_hopeless_reason_ops)) ); +TRACE_EVENT(mm_vmscan_lru_gen_walk, + + TP_PROTO(int nid, unsigned long seq, int leaf_total, + int leaf_associated, bool empty), + + TP_ARGS(nid, seq, leaf_total, leaf_associated, empty), + + TP_STRUCT__entry( + __field(int, nid) + __field(unsigned long, seq) + __field(int, leaf_total) + __field(int, leaf_associated) + __field(bool, empty) + ), + + TP_fast_assign( + __entry->nid = nid; + __entry->seq = seq; + __entry->leaf_total = leaf_total; + __entry->leaf_associated = leaf_associated; + __entry->empty = empty; + ), + + TP_printk("nid=%d seq=%lu leaf_total=%d leaf_associated=%d empty=%d", + __entry->nid, __entry->seq, __entry->leaf_total, + __entry->leaf_associated, __entry->empty) +); + #endif /* _TRACE_VMSCAN_H */ /* This part must be outside protection */ diff --git a/mm/vmscan.c b/mm/vmscan.c index 96201eae0ceb..98037a562ab6 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3590,6 +3590,8 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, if (!folio) continue; + walk->mm_stats[MM_LEAF_ASSOCIATED]++; + if (folio_test_large(folio)) { const unsigned int max_nr = (end - addr) >> PAGE_SHIFT; @@ -3688,6 +3690,8 @@ static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area if (!folio) goto next; + walk->mm_stats[MM_LEAF_ASSOCIATED]++; + if (!pmdp_test_and_clear_young_notify(vma, addr, pmd + i)) goto next; @@ -4151,8 +4155,28 @@ static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long seq, do { success = iterate_mm_list(walk, &mm); - if (mm) + if (mm) { + bool empty = false; + walk_mm(mm, walk); + /* + * A walk that traversed page tables but found no folio + * belonging to this lruvec (node+memcg) is pure waste. + */ + if (walk->mm_stats[MM_LEAF_TOTAL]) { + walk->mm_stats[MM_WALK_TOTAL]++; + if (walk->mm_stats[MM_LEAF_ASSOCIATED] == 0) { + walk->mm_stats[MM_WALK_EMPTY]++; + walk->mm_stats[MM_LEAF_EMPTY_WALKS] += + walk->mm_stats[MM_LEAF_TOTAL]; + empty = true; + } + } + trace_mm_vmscan_lru_gen_walk( + lruvec_pgdat(lruvec)->node_id, walk->seq, + walk->mm_stats[MM_LEAF_TOTAL], + walk->mm_stats[MM_LEAF_ASSOCIATED], empty); + } } while (mm); done: if (success) { @@ -5638,14 +5662,14 @@ static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec, seq_puts(m, " "); for (i = 0; i < NR_MM_STATS; i++) { - const char *s = "xxxx"; + const char *s = "xxxxxxxx"; unsigned long n = 0; if (seq == max_seq && NR_HIST_GENS == 1) { - s = "TYFA"; + s = "TYFALWEE"; n = READ_ONCE(mm_state->stats[hist][i]); } else if (seq != max_seq && NR_HIST_GENS > 1) { - s = "tyfa"; + s = "tyfalwee"; n = READ_ONCE(mm_state->stats[hist][i]); } -- 2.52.0