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Message-ID: <20241016132452epcms1p6884ae0197aa83731baa193fb5714b0d2@epcms1p6>
Date: Wed, 16 Oct 2024 22:24:52 +0900
From: 김재원 <jaewon31.kim@...sung.com>
To: Vlastimil Babka <vbabka@...e.cz>, 김재원
<jaewon31.kim@...sung.com>, "sj@...nel.org" <sj@...nel.org>,
"minchan@...nel.org" <minchan@...nel.org>, "kaleshsingh@...gle.com"
<kaleshsingh@...gle.com>, "akpm@...ux-foundation.org"
<akpm@...ux-foundation.org>
CC: "linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"jaewon31.kim@...il.com" <jaewon31.kim@...il.com>
Subject: RE: [PATCH v2] vmscan: add a vmscan event for reclaim_pages
>On 10/11/24 14:49, Jaewon Kim wrote:
>> The reclaim_folio_list uses a dummy reclaim_stat and is not being
>> used. To know the memory stat, add a new trace event. This is useful how
>> how many pages are not reclaimed or why.
>>
>> This is an example.
>> mm_vmscan_reclaim_pages: nid=0 nr_scanned=112 nr_reclaimed=112 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
>>
>> Currenlty reclaim_folio_list is only called by reclaim_pages, and
>> reclaim_pages is used by damon and madvise. In the latest Android,
>> reclaim_pages is also used by shmem to reclaim all pages in a
>> address_space.
>>
>> Signed-off-by: Jaewon Kim <jaewon31.kim@...sung.com>
>> ---
>> v2: remove reclaim_stat_add function and call the trace on each node
>> v1: introduce a new trace event
>> ---
>> include/trace/events/vmscan.h | 45 +++++++++++++++++++++++++++++++++++
>> mm/vmscan.c | 16 +++++++++----
>> 2 files changed, 56 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
>> index 1a488c30afa5..490958fa10de 100644
>> --- a/include/trace/events/vmscan.h
>> +++ b/include/trace/events/vmscan.h
>> @@ -346,6 +346,51 @@ TRACE_EVENT(mm_vmscan_write_folio,
>> show_reclaim_flags(__entry->reclaim_flags))
>> );
>>
>> +TRACE_EVENT(mm_vmscan_reclaim_pages,
>> +
>> + TP_PROTO(int nid,
>> + unsigned long nr_scanned, unsigned long nr_reclaimed,
>> + struct reclaim_stat *stat),
>> +
>> + TP_ARGS(nid, nr_scanned, nr_reclaimed, stat),
>> +
>> + TP_STRUCT__entry(
>> + __field(int, nid)
>> + __field(unsigned long, nr_scanned)
>> + __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)
>> + ),
>> +
>> + TP_fast_assign(
>> + __entry->nid = nid;
>> + __entry->nr_scanned = nr_scanned;
>> + __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;
>> + ),
>> +
>> + TP_printk("nid=%d nr_scanned=%ld nr_reclaimed=%ld nr_dirty=%ld nr_writeback=%ld nr_congested=%ld nr_immediate=%ld nr_activate_anon=%d nr_activate_file=%d nr_ref_keep=%ld nr_unmap_fail=%ld",
>> + __entry->nid,
>> + __entry->nr_scanned, __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)
>> +);
>> +
>> TRACE_EVENT(mm_vmscan_lru_shrink_inactive,
>>
>> TP_PROTO(int nid,
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index 749cdc110c74..0c2c36bf4c5a 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -2126,9 +2126,10 @@ static void shrink_active_list(unsigned long nr_to_scan,
>> }
>>
>> static unsigned int reclaim_folio_list(struct list_head *folio_list,
>> + unsigned int nr_scanned,
>> struct pglist_data *pgdat)
>> {
>> - struct reclaim_stat dummy_stat;
>> + struct reclaim_stat stat;
>> unsigned int nr_reclaimed;
>> struct folio *folio;
>> struct scan_control sc = {
>> @@ -2139,12 +2140,13 @@ static unsigned int reclaim_folio_list(struct list_head *folio_list,
>> .no_demotion = 1,
>> };
>>
>> - nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &dummy_stat, true);
>> + nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &stat, true);
>> while (!list_empty(folio_list)) {
>> folio = lru_to_folio(folio_list);
>> list_del(&folio->lru);
>> folio_putback_lru(folio);
>> }
>> + trace_mm_vmscan_reclaim_pages(pgdat->node_id, nr_scanned, nr_reclaimed, &stat);
>
>Why is the new calculation of nr_scanned needed? Could you just take a delta
>of sc->nr_scanned, i.e. after - before calling shrink_folio_list() ?
Oh correct.
Except the case of (!folio_trylock(folio)), shrink_folio_list would count on sc->nr_scanned.
I don't understand why we do not count this lock case though.
Let me try to change as you suggested.
I think without 'after - before', we can just use sc->nr_scanned after shrink_folio_list.
Thank you
>
>>
>> return nr_reclaimed;
>> }
>> @@ -2152,6 +2154,7 @@ static unsigned int reclaim_folio_list(struct list_head *folio_list,
>> unsigned long reclaim_pages(struct list_head *folio_list)
>> {
>> int nid;
>> + unsigned int nr_scanned = 0;
>> unsigned int nr_reclaimed = 0;
>> LIST_HEAD(node_folio_list);
>> unsigned int noreclaim_flag;
>> @@ -2168,15 +2171,18 @@ unsigned long reclaim_pages(struct list_head *folio_list)
>> if (nid == folio_nid(folio)) {
>> folio_clear_active(folio);
>> list_move(&folio->lru, &node_folio_list);
>> + nr_scanned += folio_nr_pages(folio);
>> continue;
>> }
>>
>> - nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
>> + nr_reclaimed += reclaim_folio_list(&node_folio_list, nr_scanned,
>> + NODE_DATA(nid));
>> + nr_scanned = 0;
>> nid = folio_nid(lru_to_folio(folio_list));
>> } while (!list_empty(folio_list));
>>
>> - nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
>> -
>> + nr_reclaimed += reclaim_folio_list(&node_folio_list, nr_scanned,
>> + NODE_DATA(nid));
>> memalloc_noreclaim_restore(noreclaim_flag);
>>
>> return nr_reclaimed;
>
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