On Fri, Mar 1, 2019 at 11:54 AM Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
>
> In the page alloc fast path, it may do node reclaim, which may cause
> latency spike.
> We should add tracepoint for this event, and also measure the latency
> it causes.
>
> So bellow two tracepoints are introduced,
> mm_vmscan_node_reclaim_begin
> mm_vmscan_node_reclaim_end
>
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Acked-by: Souptick Joarder <jrdr.linux@xxxxxxxxx>
(for the comment on v1).
> ---
> include/trace/events/vmscan.h | 32 ++++++++++++++++++++++++++++++++
> mm/vmscan.c | 6 ++++++
> 2 files changed, 38 insertions(+)
>
> diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
> index a1cb913..c1ddf28 100644
> --- a/include/trace/events/vmscan.h
> +++ b/include/trace/events/vmscan.h
> @@ -465,6 +465,38 @@
> __entry->ratio,
> show_reclaim_flags(__entry->reclaim_flags))
> );
> +
> +TRACE_EVENT(mm_vmscan_node_reclaim_begin,
> +
> + TP_PROTO(int nid, int order, gfp_t gfp_flags),
> +
> + TP_ARGS(nid, order, gfp_flags),
> +
> + TP_STRUCT__entry(
> + __field(int, nid)
> + __field(int, order)
> + __field(gfp_t, gfp_flags)
> + ),
> +
> + TP_fast_assign(
> + __entry->nid = nid;
> + __entry->order = order;
> + __entry->gfp_flags = gfp_flags;
> + ),
> +
> + TP_printk("nid=%d order=%d gfp_flags=%s",
> + __entry->nid,
> + __entry->order,
> + show_gfp_flags(__entry->gfp_flags))
> +);
> +
> +DEFINE_EVENT(mm_vmscan_direct_reclaim_end_template, mm_vmscan_node_reclaim_end,
> +
> + TP_PROTO(unsigned long nr_reclaimed),
> +
> + TP_ARGS(nr_reclaimed)
> +);
> +
> #endif /* _TRACE_VMSCAN_H */
>
> /* This part must be outside protection */
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index ac4806f..2bee5d1 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -4241,6 +4241,9 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
> .reclaim_idx = gfp_zone(gfp_mask),
> };
>
> + trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order,
> + sc.gfp_mask);
> +
> cond_resched();
> fs_reclaim_acquire(sc.gfp_mask);
> /*
> @@ -4267,6 +4270,9 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
> current->flags &= ~PF_SWAPWRITE;
> memalloc_noreclaim_restore(noreclaim_flag);
> fs_reclaim_release(sc.gfp_mask);
> +
> + trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed);
> +
> return sc.nr_reclaimed >= nr_pages;
> }
>
> --
> 1.8.3.1
>
