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Message-ID: <8d96e6ec-5299-4b56-9795-18d690b6e77e@suse.cz>
Date: Wed, 16 Oct 2024 15:03:32 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Jaewon Kim <jaewon31.kim@...sung.com>, sj@...nel.org, minchan@...nel.org,
kaleshsingh@...gle.com, akpm@...ux-foundation.org
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, 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() ?
>
> 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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