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[209.85.220.65]) by mx.google.com with SMTPS id b19sor9803255ioj.10.2019.02.28.02.35.12 for (Google Transport Security); Thu, 28 Feb 2019 02:35:12 -0800 (PST) Received-SPF: pass (google.com: domain of laoar.shao@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=Zoxgixcq; spf=pass (google.com: domain of laoar.shao@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=laoar.shao@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=n1j+98FSrDpg32f5NKLaFgL1Gb2pNFMygOJPoirCPZ8=; b=ZoxgixcqqpaGMnZErw+ZFXETvifrkWXV36/v8DFcYgraF7z5rn6r1O3a0vVfoJwvYi iX/j0J5qJGTxUwJwf7hunG3EjLKIz2o5pSQYTa+r6+6LpQxYJszeT7IyK0LDj+6xIiOB odQMkL5Ikj92QCUY9XQnX9oMJwsKALnTR1z07o68ej5YMyARCPVJRJyBNFde/buqmBQ1 1Iz393qJ2kimSySzfyn78LRlI84A1HW1oWr3UE3sfPgtT+73aFigEACeq/UbP1d5tMwm gdEGPCNKzTFORIHz/5czMZTz9+jh+Qks2vY2rEGyPiOJ5GVhDXJPdwthR10mOhCyKll8 3o4A== X-Google-Smtp-Source: APXvYqyIMk8ZnpDTyjU7ltGUPgrLHGGy1U7PRvyYe8IRIcfjek3M5QszGr8lxPVac4ySk5dmQdnjDKXqpFA3rByJV88= X-Received: by 2002:a5d:84c3:: with SMTP id z3mr4808892ior.11.1551350111830; Thu, 28 Feb 2019 02:35:11 -0800 (PST) MIME-Version: 1.0 References: <1551341664-13912-1-git-send-email-laoar.shao@gmail.com> <2cf3574c-34f9-ada8-d27c-1ed822031305@suse.cz> In-Reply-To: <2cf3574c-34f9-ada8-d27c-1ed822031305@suse.cz> From: Yafang Shao Date: Thu, 28 Feb 2019 18:34:35 +0800 Message-ID: Subject: Re: [PATCH] mm: vmscan: add tracepoints for node reclaim To: Vlastimil Babka Cc: Andrew Morton , Michal Hocko , ktkhai@virtuozzo.com, broonie@kernel.org, Johannes Weiner , Linux MM , shaoyafang@didiglobal.com Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Feb 28, 2019 at 6:21 PM Vlastimil Babka 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 > > --- > > 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. Seems we'd better drop them from other tracepoints as well ? > > + ), > > + > > + TP_fast_assign( > > + __entry->nid = nid; > > + __entry->order = order; > > + __entry->may_writepage = may_writepage; > > + __entry->gfp_flags = gfp_flags; > > + __entry->zid = zid; > > + ), > > + > > + TP_printk("nid=%d zid=%d order=%d may_writepage=%d gfp_flags=%s", > > + __entry->nid, > > + __entry->zid, > > + __entry->order, > > + __entry->may_writepage, > > + show_gfp_flags(__entry->gfp_flags)) > > +); > > + > > +TRACE_EVENT(mm_vmscan_node_reclaim_end, > > + > > + TP_PROTO(int result), > > + > > + TP_ARGS(result), > > + > > + TP_STRUCT__entry( > > + __field(int, result) > > Reporting sc.nr_reclaimed sounds more useful and in line with other > reclaim tracepoints. Result (sc.nr_reclaimed >= nr_pages) can then be > derived by postprocessing as the beginning tracepoint contains 'order' > thus we know nr_pages? > Seems reasonable. Will change it. > > + ), > > + > > + TP_fast_assign( > > + __entry->result = result; > > + ), > > + > > + TP_printk("result=%d", __entry->result) > > +); > > #endif /* _TRACE_VMSCAN_H */ > > > > /* This part must be outside protection */ > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index ac4806f..01a0401 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -4240,6 +4240,12 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in > > .may_swap = 1, > > .reclaim_idx = gfp_zone(gfp_mask), > > }; > > + int result; > > + > > + trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order, > > + sc.may_writepage, > > + sc.gfp_mask, > > + sc.reclaim_idx); > > > > cond_resched(); > > fs_reclaim_acquire(sc.gfp_mask); > > @@ -4267,7 +4273,12 @@ 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); > > - return sc.nr_reclaimed >= nr_pages; > > + > > + result = sc.nr_reclaimed >= nr_pages; > > + > > + trace_mm_vmscan_node_reclaim_end(result); > > + > > + return result; > > } > > > > int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) > > > Thanks Yafang