RE: [PATCH v4] vmscan: add trace events for lru_gen

[김재원]

>>On Mon, Sep 25, 2023 at 10:20?PM Jaewon Kim <jaewon31.kim@xxxxxxxxxxx> wrote:
>>>
>>> As the legacy lru provides, the lru_gen needs some trace events for
>>> debugging.
>>>
>>> This commit introduces 2 trace events.
>>>   trace_mm_vmscan_lru_gen_scan
>>>   trace_mm_vmscan_lru_gen_evict
>>>
>>> Each event is similar to the following legacy events.
>>>   trace_mm_vmscan_lru_isolate,
>>>   trace_mm_vmscan_lru_shrink_[in]active
>>
>>We should just reuse trace_mm_vmscan_lru_isolate and
>>trace_mm_vmscan_lru_shrink_inactive instead of adding new tracepoints.
>>
>>To reuse trace_mm_vmscan_lru_isolate, we'd just need to append two new
>>names to LRU_NAMES.
>>
>>The naming of trace_mm_vmscan_lru_shrink_inactive might seem confusing
>>but it's how MGLRU maintains the compatibility, e.g., the existing
>>active/inactive counters in /proc/vmstat.
>
>
>Hello
>
>Actually I had tried to reuse them. But some value was not that compatible.
>Let me try that way again.
>
>>

Hello Yu Zhao

Could you look into what I tried below? I reused the legacy trace events as you recommened.

For the nr_scanned for trace_mm_vmscan_lru_shrink_inactive, I just used the scanned returned from isolate_folios.
I thought this is right as scan_folios also uses its isolated.
  __count_vm_events(PGSCAN_ANON + type, isolated);
But I guess the scanned in scan_folios is actually the one used in shrink_inactive_list

I tested this on both 0 and 7 of /sys/kernel/mm/lru_gen/enabled


diff --git a/mm/vmscan.c b/mm/vmscan.c
index a4e44f1c97c1..b61a0156559c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4328,6 +4328,7 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
        int sorted = 0;
        int scanned = 0;
        int isolated = 0;
+       int skipped = 0;
        int remaining = MAX_LRU_BATCH;
        struct lru_gen_folio *lrugen = &lruvec->lrugen;
        struct mem_cgroup *memcg = lruvec_memcg(lruvec);
@@ -4341,7 +4342,7 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
 
        for (i = MAX_NR_ZONES; i > 0; i--) {
                LIST_HEAD(moved);
-               int skipped = 0;
+               int skipped_zone = 0;
                int zone = (sc->reclaim_idx + i) % MAX_NR_ZONES;
                struct list_head *head = &lrugen->folios[gen][type][zone];
 
@@ -4363,16 +4364,17 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
                                isolated += delta;
                        } else {
                                list_move(&folio->lru, &moved);
-                               skipped += delta;
+                               skipped_zone += delta;
                        }
 
-                       if (!--remaining || max(isolated, skipped) >= MIN_LRU_BATCH)
+                       if (!--remaining || max(isolated, skipped_zone) >= MIN_LRU_BATCH)
                                break;
                }
 
-               if (skipped) {
+               if (skipped_zone) {
                        list_splice(&moved, head);
-                       __count_zid_vm_events(PGSCAN_SKIP, zone, skipped);
+                       __count_zid_vm_events(PGSCAN_SKIP, zone, skipped_zone);
+                       skipped += skipped_zone;
                }
 
                if (!remaining || isolated >= MIN_LRU_BATCH)
@@ -4387,6 +4389,9 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
        __count_memcg_events(memcg, item, isolated);
        __count_memcg_events(memcg, PGREFILL, sorted);
        __count_vm_events(PGSCAN_ANON + type, isolated);
+       trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, MAX_LRU_BATCH,
+                                   scanned, skipped, isolated,
+                                   type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
 
        /*
         * There might not be eligible folios due to reclaim_idx. Check the
@@ -4517,6 +4522,9 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
 retry:
        reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false);
        sc->nr_reclaimed += reclaimed;
+       trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
+                       scanned, reclaimed, &stat, sc->priority,
+                       type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
 
        list_for_each_entry_safe_reverse(folio, next, &list, lru) {
                if (!folio_evictable(folio)) {



>>> Here's an example
>>>   mm_vmscan_lru_gen_scan: classzone=2 order=0 nr_requested=4096 nr_scanned=64 nr_skipped=0 nr_taken=64 lru=anon
>>>   mm_vmscan_lru_gen_evict: nid=0 nr_reclaimed=64 nr_dirty=0 nr_writeback=0 nr_congested=0 nr_immediate=0 nr_activate_anon=0 nr_activate_file=0 nr_ref_keep=0 nr_unmap_fail=0 priority=2 flags=RECLAIM_WB_ANON|RECLAIM_WB_ASYNC
>>>   mm_vmscan_lru_gen_scan: classzone=1 order=0 nr_requested=4096 nr_scanned=64 nr_skipped=0 nr_taken=64 lru=file
>>>   mm_vmscan_lru_gen_evict: nid=0 nr_reclaimed=64 nr_dirty=0 nr_writeback=0 nr_congested=0 nr_immediate=0 nr_activate_anon=0 nr_activate_file=0 nr_ref_keep=0 nr_unmap_fail=0 priority=12 flags=RECLAIM_WB_FILE|RECLAIM_WB_ASYNC
>>>
>>> Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
>>> ---
>>> v4: wrap with #ifdef CONFIG_LRU_GEN
>>> v3: change printk format
>>> v2: use condition and make it aligned
>>> v1: introduce trace events
>>> ---
>>>  include/trace/events/mmflags.h |  9 ++++
>>>  include/trace/events/vmscan.h  | 96 ++++++++++++++++++++++++++++++++++
>>>  mm/vmscan.c                    | 20 +++++--
>>>  3 files changed, 120 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
>>> index 1478b9dd05fa..6dfe85bd4e81 100644
>>> --- a/include/trace/events/mmflags.h
>>> +++ b/include/trace/events/mmflags.h
>>> @@ -274,6 +274,12 @@ IF_HAVE_VM_SOFTDIRTY(VM_SOFTDIRTY, "softdirty"     )               \
>>>                 EM (LRU_ACTIVE_FILE, "active_file") \
>>>                 EMe(LRU_UNEVICTABLE, "unevictable")
>>>
>>> +#ifdef CONFIG_LRU_GEN
>>> +#define LRU_GEN_NAMES          \
>>> +               EM (LRU_GEN_ANON, "anon") \
>>> +               EMe(LRU_GEN_FILE, "file")
>>> +#endif
>>> +
>>>  /*
>>>   * First define the enums in the above macros to be exported to userspace
>>>   * via TRACE_DEFINE_ENUM().
>>> @@ -288,6 +294,9 @@ COMPACTION_PRIORITY
>>>  /* COMPACTION_FEEDBACK are defines not enums. Not needed here. */
>>>  ZONE_TYPE
>>>  LRU_NAMES
>>> +#ifdef CONFIG_LRU_GEN
>>> +LRU_GEN_NAMES
>>> +#endif
>>>
>>>  /*
>>>   * Now redefine the EM() and EMe() macros to map the enums to the strings
>>> diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
>>> index d2123dd960d5..2080ef742f89 100644
>>> --- a/include/trace/events/vmscan.h
>>> +++ b/include/trace/events/vmscan.h
>>> @@ -327,6 +327,102 @@ TRACE_EVENT(mm_vmscan_lru_isolate,
>>>                 __print_symbolic(__entry->lru, LRU_NAMES))
>>>  );
>>>
>>> +#ifdef CONFIG_LRU_GEN
>>> +TRACE_EVENT_CONDITION(mm_vmscan_lru_gen_scan,
>>> +       TP_PROTO(int highest_zoneidx,
>>> +               int order,
>>> +               unsigned long nr_requested,
>>> +               unsigned long nr_scanned,
>>> +               unsigned long nr_skipped,
>>> +               unsigned long nr_taken,
>>> +               int lru),
>>> +
>>> +       TP_ARGS(highest_zoneidx, order, nr_requested, nr_scanned, nr_skipped, nr_taken, lru),
>>> +
>>> +       TP_CONDITION(nr_scanned),
>>> +
>>> +       TP_STRUCT__entry(
>>> +               __field(int, highest_zoneidx)
>>> +               __field(int, order)
>>> +               __field(unsigned long, nr_requested)
>>> +               __field(unsigned long, nr_scanned)
>>> +               __field(unsigned long, nr_skipped)
>>> +               __field(unsigned long, nr_taken)
>>> +               __field(int, lru)
>>> +       ),
>>> +
>>> +       TP_fast_assign(
>>> +               __entry->highest_zoneidx = highest_zoneidx;
>>> +               __entry->order = order;
>>> +               __entry->nr_requested = nr_requested;
>>> +               __entry->nr_scanned = nr_scanned;
>>> +               __entry->nr_skipped = nr_skipped;
>>> +               __entry->nr_taken = nr_taken;
>>> +               __entry->lru = lru;
>>> +       ),
>>> +
>>> +       /*
>>> +        * classzone is previous name of the highest_zoneidx.
>>> +        * Reason not to change it is the ABI requirement of the tracepoint.
>>> +        */
>>> +       TP_printk("classzone=%d order=%d nr_requested=%lu nr_scanned=%lu nr_skipped=%lu nr_taken=%lu lru=%s",
>>> +               __entry->highest_zoneidx,
>>> +               __entry->order,
>>> +               __entry->nr_requested,
>>> +               __entry->nr_scanned,
>>> +               __entry->nr_skipped,
>>> +               __entry->nr_taken,
>>> +               __print_symbolic(__entry->lru, LRU_GEN_NAMES))
>>> +);
>>> +
>>> +TRACE_EVENT(mm_vmscan_lru_gen_evict,
>>> +
>>> +       TP_PROTO(int nid, unsigned long nr_reclaimed,
>>> +               struct reclaim_stat *stat, int priority, int file),
>>> +
>>> +       TP_ARGS(nid, nr_reclaimed, stat, priority, file),
>>> +
>>> +       TP_STRUCT__entry(
>>> +               __field(unsigned long, nr_reclaimed)
>>> +               __field(unsigned long, nr_dirty)
>>> +               __field(unsigned long, nr_writeback)
>>> +               __field(unsigned long, nr_congested)
>>> +               __field(unsigned long, nr_immediate)
>>> +               __field(unsigned int, nr_activate0)
>>> +               __field(unsigned int, nr_activate1)
>>> +               __field(unsigned long, nr_ref_keep)
>>> +               __field(unsigned long, nr_unmap_fail)
>>> +               __field(int, nid)
>>> +               __field(int, priority)
>>> +               __field(int, reclaim_flags)
>>> +       ),
>>> +
>>> +       TP_fast_assign(
>>> +               __entry->nid = nid;
>>> +               __entry->nr_reclaimed = nr_reclaimed;
>>> +               __entry->nr_dirty = stat->nr_dirty;
>>> +               __entry->nr_writeback = stat->nr_writeback;
>>> +               __entry->nr_congested = stat->nr_congested;
>>> +               __entry->nr_immediate = stat->nr_immediate;
>>> +               __entry->nr_activate0 = stat->nr_activate[0];
>>> +               __entry->nr_activate1 = stat->nr_activate[1];
>>> +               __entry->nr_ref_keep = stat->nr_ref_keep;
>>> +               __entry->nr_unmap_fail = stat->nr_unmap_fail;
>>> +               __entry->priority = priority;
>>> +               __entry->reclaim_flags = trace_reclaim_flags(file);
>>> +       ),
>>> +
>>> +       TP_printk("nid=%d nr_reclaimed=%lu nr_dirty=%lu nr_writeback=%lu nr_congested=%lu nr_immediate=%lu nr_activate_anon=%u nr_activate_file=%u nr_ref_keep=%lu nr_unmap_fail=%lu priority=%d flags=%s",
>>> +               __entry->nid, __entry->nr_reclaimed,
>>> +               __entry->nr_dirty, __entry->nr_writeback,
>>> +               __entry->nr_congested, __entry->nr_immediate,
>>> +               __entry->nr_activate0, __entry->nr_activate1,
>>> +               __entry->nr_ref_keep, __entry->nr_unmap_fail,
>>> +               __entry->priority,
>>> +               show_reclaim_flags(__entry->reclaim_flags))
>>> +);
>>> +#endif
>>> +
>>>  TRACE_EVENT(mm_vmscan_write_folio,
>>>
>>>         TP_PROTO(struct folio *folio),
>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>> index 6f13394b112e..0c8b48bcb461 100644
>>> --- a/mm/vmscan.c
>>> +++ b/mm/vmscan.c
>>> @@ -5005,6 +5005,7 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
>>>         int sorted = 0;
>>>         int scanned = 0;
>>>         int isolated = 0;
>>> +       int skipped = 0;
>>>         int remaining = MAX_LRU_BATCH;
>>>         struct lru_gen_folio *lrugen = &lruvec->lrugen;
>>>         struct mem_cgroup *memcg = lruvec_memcg(lruvec);
>>> @@ -5018,7 +5019,7 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
>>>
>>>         for (i = MAX_NR_ZONES; i > 0; i--) {
>>>                 LIST_HEAD(moved);
>>> -               int skipped = 0;
>>> +               int skipped_zone = 0;
>>>                 int zone = (sc->reclaim_idx + i) % MAX_NR_ZONES;
>>>                 struct list_head *head = &lrugen->folios[gen][type][zone];
>>>
>>> @@ -5040,16 +5041,17 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
>>>                                 isolated += delta;
>>>                         } else {
>>>                                 list_move(&folio->lru, &moved);
>>> -                               skipped += delta;
>>> +                               skipped_zone += delta;
>>>                         }
>>>
>>> -                       if (!--remaining || max(isolated, skipped) >= MIN_LRU_BATCH)
>>> +                       if (!--remaining || max(isolated, skipped_zone) >= MIN_LRU_BATCH)
>>>                                 break;
>>>                 }
>>>
>>> -               if (skipped) {
>>> +               if (skipped_zone) {
>>>                         list_splice(&moved, head);
>>> -                       __count_zid_vm_events(PGSCAN_SKIP, zone, skipped);
>>> +                       __count_zid_vm_events(PGSCAN_SKIP, zone, skipped_zone);
>>> +                       skipped += skipped_zone;
>>>                 }
>>>
>>>                 if (!remaining || isolated >= MIN_LRU_BATCH)
>>> @@ -5065,6 +5067,10 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
>>>         __count_memcg_events(memcg, PGREFILL, sorted);
>>>         __count_vm_events(PGSCAN_ANON + type, isolated);
>>>
>>> +#ifdef CONFIG_LRU_GEN
>>> +       trace_mm_vmscan_lru_gen_scan(sc->reclaim_idx, sc->order, MAX_LRU_BATCH,
>>> +                       scanned, skipped, isolated, type);
>>> +#endif
>>
>>These functions are already within CONFIG_LRU_GEN.
>>
>>>         /*
>>>          * There might not be eligible folios due to reclaim_idx. Check the
>>>          * remaining to prevent livelock if it's not making progress.
>>> @@ -5194,6 +5200,10 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
>>>  retry:
>>>         reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false);
>>>         sc->nr_reclaimed += reclaimed;
>>> +#ifdef CONFIG_LRU_GEN
>>> +       trace_mm_vmscan_lru_gen_evict(pgdat->node_id, reclaimed, &stat,
>>> +                                     sc->priority, type);
>>> +#endif
>>
>>Ditto.