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[209.85.220.41]) by mx.google.com with SMTPS id s6sor4386620qtq.34.2019.07.10.11.21.34 for (Google Transport Security); Wed, 10 Jul 2019 11:21:34 -0700 (PDT) Received-SPF: pass (google.com: domain of shy828301@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=EmzFHtYR; spf=pass (google.com: domain of shy828301@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=shy828301@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:content-transfer-encoding; bh=vaM/jDV0vwnZcpeTJQx+SNo6Abxw5kOZNK++pSNNKbs=; b=EmzFHtYR5s/7FzftX73JyWNWe1gQKt9q2QKmCdU683LuU4dkvC9Yg/jt3kGDQZ30A3 tVYmKfvOul5/+g0vkHsIOJbl1c39hvRThPP1RE2VNegulSiWqLW4sVZgGvpKLr83RMjP GQEaYvO6PsWRUjjMJQS4Gd3uJr9l7hWaTKajaJKscDdqRAlLRgFY/jpHeuW1o0QREa8N r3riiQK6og8NhF2PTPFt+Wd66HAzMMvBAGMhGiog/y4kM3NrOFj1V0QIvK7iiY6Zxmyl Ih5a/4/nczJ8VP/QIrPoh037t3NcuZyn+As6NWR9gnWhqUDWfXY7xgffDXRyAKg60hGe oQ9Q== X-Google-Smtp-Source: APXvYqwhymDEm77SIkns9B8wc1lKNrsfxnW9NBqSXp4VKy6EVvLCYpla9dXa1RZ322N03KEbau2RsEAvQMeD5eFdUT8= X-Received: by 2002:ac8:f3b:: with SMTP id e56mr25390354qtk.123.1562782894620; Wed, 10 Jul 2019 11:21:34 -0700 (PDT) MIME-Version: 1.0 References: <20190710144138.qyn4tuttdq6h7kqx@linutronix.de> In-Reply-To: <20190710144138.qyn4tuttdq6h7kqx@linutronix.de> From: Yang Shi Date: Wed, 10 Jul 2019 11:21:19 -0700 Message-ID: Subject: Re: Memory compaction and mlockall() To: Sebastian Andrzej Siewior Cc: Linux MM , Thomas Gleixner Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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 Wed, Jul 10, 2019 at 7:41 AM Sebastian Andrzej Siewior wrote: > > Hi, > > I've been looking at the following trace: > | cyclicte-526 0d...2.. 6876070 603us : finish_task_switch <-__schedu= le > | cyclicte-526 0....2.. 6876070 605us : preempt_count_sub <-finish_ta= sk_switch > | cyclicte-526 0....1.. 6876070 607us : preempt_count_sub <-schedule > | cyclicte-526 0....... 6876070 610us : finish_wait <-put_and_wait_on= _page_locked > > I see put_and_wait_on_page_locked after schedule and didn't expect that. > cyclictest then blocks on a lock and switches to `kcompact'. Once it > finishes, it switches back to cyclictest: > | cyclicte-526 0....... 6876070 853us : rt_spin_unlock <-put_and_wait= _on_page_locked > | cyclicte-526 0....... 6876070 854us : migrate_enable <-rt_spin_unlo= ck > | cyclicte-526 0....... 6876070 860us : up_read <-do_page_fault > | cyclicte-526 0....... 6876070 861us : __up_read <-do_page_fault > | cyclicte-526 0d...... 6876070 867us : do_PrefetchAbort <-ret_from_e= xception > | cyclicte-526 0d...... 6876070 868us : do_page_fault <-do_PrefetchAb= ort > | cyclicte-526 0....... 6876070 870us : down_read_trylock <-do_page_f= ault > | cyclicte-526 0....... 6876070 872us : __down_read_trylock <-do_page= _fault > =E2=80=A6 > | cyclicte-526 0....... 6876070 914us : __up_read <-do_page_fault > | cyclicte-526 0....... 6876070 923us : sys_clock_gettime32 <-ret_fas= t_syscall > | cyclicte-526 0....... 6876070 925us : posix_ktime_get_ts <-sys_cloc= k_gettime32 > > I did not expect a pagefault with mlockall(). I assume it has to do with > memory compaction. I have > | CONFIG_COMPACTION=3Dy > | CONFIG_MIGRATION=3Dy > > and Kconfig says: > |config COMPACTION > =E2=80=A6 > | You shouldn't > | disable this option unless there really is a strong reason fo= r > | it and then we would be really interested to hear about that = at > | linux-mm@kvack.org. > > Shouldn't COMPACTION avoid touching/moving mlock()ed pages? compaction should not isolate unevictable pages unless you have /proc/sys/vm/compact_unevictable_allowed set. > > Sebastian >