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[209.85.220.65]) by mx.google.com with SMTPS id p16sor9891863ios.4.2019.02.28.02.49.22 for (Google Transport Security); Thu, 28 Feb 2019 02:49:22 -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=VNcte+ku; 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=RB/VMG7u60T8INZFCvvnDZ76dB6R/WBXxH/BFSAbgTc=; b=VNcte+kudUAgGFlzPWV/+negJWt9tSI822DcsA6XvaRIzZ/0OCn7ShZj9+GbHnTACW vpG9QSjnRZiY4UKJVzb4VtRuKeGhnZzdEz1AjAECKMFOg2ZEk2fSMUaUDiFfEV1TnFHs AEvprkZ34cdinNf+bcRpFr1bFAkLVOPWEAkn3UsBil6A/iC+c/WgUu/dRWqdC7F6EOa/ zEDj6zNCHhC+hY5ork7WJoH2E9Zl39L4P4ZWLVABTyca1uTSVgnRNGVq3/MUgnXAhP2j EGYOytwd6Ahcga6jQdCS3Z0dxKX/ctfJahCACWvRg/1Ln/GQhJQPPT6eOST1LTMZ+YW4 m99A== X-Google-Smtp-Source: APXvYqyelUV/wLnvoJFHXRX1SlIBCvX7nHv+L8iv3g9+CU7GW2pb83qaNwRo5c5AFlkivX+ls+v+VDrI3r+nbHKMjIY= X-Received: by 2002:a5d:84c3:: with SMTP id z3mr4836173ior.11.1551350962573; Thu, 28 Feb 2019 02:49:22 -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: From: Yafang Shao Date: Thu, 28 Feb 2019 18:48:46 +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 6:44 PM Vlastimil Babka wrote: > > On 2/28/19 11:34 AM, Yafang Shao wrote: > > 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. > > I see zid only in kswapd waking tracepoints? That's different kind of > event. > Pls. see mm_vmscan_wakeup_kswapd and classzone_idx in mm_vmscan_direct_reclaim_begin_template. mm_vmscan_direct_reclaim_begin_template: "order=%d may_writepage=%d gfp_flags=%s classzone_idx=%d" mm_vmscan_wakeup_kswapd: "nid=%d zid=%d order=%d gfp_flags=%s" > > 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. OK. Thanks Yafang