From: Yang Shi <shy828301@gmail.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Linux MM <linux-mm@kvack.org>, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: Memory compaction and mlockall()
Date: Wed, 10 Jul 2019 11:21:19 -0700 [thread overview]
Message-ID: <CAHbLzkpME1oT2=-TNPm9S_iZ2nkGsY6AXo7iVgDUhg8WysDpZw@mail.gmail.com> (raw)
In-Reply-To: <20190710144138.qyn4tuttdq6h7kqx@linutronix.de>
On Wed, Jul 10, 2019 at 7:41 AM Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
>
> Hi,
>
> I've been looking at the following trace:
> | cyclicte-526 0d...2.. 6876070 603us : finish_task_switch <-__schedule
> | cyclicte-526 0....2.. 6876070 605us : preempt_count_sub <-finish_task_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_unlock
> | 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_exception
> | cyclicte-526 0d...... 6876070 868us : do_page_fault <-do_PrefetchAbort
> | cyclicte-526 0....... 6876070 870us : down_read_trylock <-do_page_fault
> | cyclicte-526 0....... 6876070 872us : __down_read_trylock <-do_page_fault
> …
> | cyclicte-526 0....... 6876070 914us : __up_read <-do_page_fault
> | cyclicte-526 0....... 6876070 923us : sys_clock_gettime32 <-ret_fast_syscall
> | cyclicte-526 0....... 6876070 925us : posix_ktime_get_ts <-sys_clock_gettime32
>
> I did not expect a pagefault with mlockall(). I assume it has to do with
> memory compaction. I have
> | CONFIG_COMPACTION=y
> | CONFIG_MIGRATION=y
>
> and Kconfig says:
> |config COMPACTION
> …
> | You shouldn't
> | disable this option unless there really is a strong reason for
> | 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
>
next prev parent reply other threads:[~2019-07-10 18:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-10 14:41 Memory compaction and mlockall() Sebastian Andrzej Siewior
2019-07-10 16:20 ` Dave Hansen
2019-07-10 16:45 ` Sebastian Andrzej Siewior
2019-07-10 17:02 ` Dave Hansen
2019-07-10 18:21 ` Yang Shi [this message]
2019-07-11 9:43 ` Sebastian Andrzej Siewior
2019-07-11 16:23 ` Yang Shi
2019-08-12 14:59 ` Vlastimil Babka
2019-08-12 15:54 ` Sebastian Andrzej Siewior
2019-08-13 8:23 ` Vlastimil Babka
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