On 2/28/19 11:34 AM, Yafang Shao wrote: > On Thu, Feb 28, 2019 at 6:21 PM Vlastimil Babka <vbabka@xxxxxxx> wrote: >> >> On 2/28/19 9:14 AM, Yafang Shao 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 mesure 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> >>> --- >>> include/trace/events/vmscan.h | 48 +++++++++++++++++++++++++++++++++++++++++++ >>> mm/vmscan.c | 13 +++++++++++- >>> 2 files changed, 60 insertions(+), 1 deletion(-) >>> >>> diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h >>> index a1cb913..9310d5b 100644 >>> --- a/include/trace/events/vmscan.h >>> +++ b/include/trace/events/vmscan.h >>> @@ -465,6 +465,54 @@ >>> __entry->ratio, >>> show_reclaim_flags(__entry->reclaim_flags)) >>> ); >>> + >>> +TRACE_EVENT(mm_vmscan_node_reclaim_begin, >>> + >>> + TP_PROTO(int nid, int order, int may_writepage, >>> + gfp_t gfp_flags, int zid), >>> + >>> + TP_ARGS(nid, order, may_writepage, gfp_flags, zid), >>> + >>> + TP_STRUCT__entry( >>> + __field(int, nid) >>> + __field(int, order) >>> + __field(int, may_writepage) >> >> For node reclaim may_writepage is statically set in node_reclaim_mode, >> so I'm not sure it's worth including it. >> >>> + __field(gfp_t, gfp_flags) >>> + __field(int, zid) >> >> zid seems wasteful and misleading as it's simply derived by >> gfp_zone(gfp_mask), so I would drop it. >> > > I agree with you that may_writepage and zid is wasteful, but I found > they are in other tracepoints in this file, > so I place them in this tracepoint as well. I see zid only in kswapd waking tracepoints? That's different kind of event. > Seems we'd better drop them from other tracepoints as well ? Hmm seems may_writepage in other tracepoints depends on laptop_mode which is also a static setting. do_try_to_free_pages() can override it due to priority, but that doesn't affect the tracepoints. If they are to be dropped, it would be a separate patch though.
