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From: Pavel Tatashin <pasha.tatashin@soleen.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Vijay Balakrishna <vijayb@linux.microsoft.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Oleg Nesterov <oleg@redhat.com>, Song Liu <songliubraving@fb.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Allen Pais <apais@microsoft.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>
Subject: Re: [[PATCH]] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged
Date: Thu, 10 Sep 2020 18:28:29 -0400	[thread overview]
Message-ID: <CA+CK2bACLNVqKP9Mgr37HQKOY=7+-PwuLCtqN6+saW7uuiMCfw@mail.gmail.com> (raw)
In-Reply-To: <20200910220145.5j7iogqulmvg5vr6@black.fi.intel.com>

Hi Kirill,

On Thu, Sep 10, 2020 at 6:01 PM Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> On Thu, Sep 10, 2020 at 01:47:39PM -0700, Vijay Balakrishna wrote:
> > When memory is hotplug added or removed the min_free_kbytes must be
> > recalculated based on what is expected by khugepaged.  Currently
> > after hotplug, min_free_kbytes will be set to a lower default and higher
> > default set when THP enabled is lost. This leaves the system with small
> > min_free_kbytes which isn't suitable for systems especially with network
> > intensive loads.  Typical failure symptoms include HW WATCHDOG reset,
> > soft lockup hang notices, NETDEVICE WATCHDOG timeouts, and OOM process
> > kills.
> >
> > Fixes: f000565adb77 ("thp: set recommended min free kbytes")
> >
> > Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
> > Cc: stable@vger.kernel.org
>
> NAK. It would override min_free_kbytes set by user.

Hi Kirill,

Thank you for looking into this. How is this different from when
khugepaged modifies it?

echo always >/sys/kernel/mm/transparent_hugepage/enabled

Which results in:

start_stop_khugepaged
  set_recommended_min_free_kbytes

Which will also adjust min_free_kbytes according to hugepaged requirement?

This bug that Vijay described is another hot-plug related issue that
we have found on our system where we perform memory hot add and hot
remove on every reboot.

Thank you,
Pasha

  reply	other threads:[~2020-09-10 22:29 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-10 20:47 [[PATCH]] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged Vijay Balakrishna
2020-09-10 22:01 ` Kirill A. Shutemov
2020-09-10 22:28   ` Pavel Tatashin [this message]
2020-09-10 22:28     ` Pavel Tatashin
2020-09-10 22:56     ` Vijay Balakrishna
2020-09-15  5:04   ` Vijay Balakrishna
2020-09-14 14:33 ` Michal Hocko
2020-09-14 16:57   ` Vijay Balakrishna
2020-09-15  8:18     ` Michal Hocko
2020-09-15 15:48       ` Vijay Balakrishna
2020-09-16  6:53         ` Michal Hocko
2020-09-16 18:28           ` Vijay Balakrishna
2020-09-17 12:12             ` Michal Hocko
2020-09-17 18:03               ` Vijay Balakrishna
2020-09-18  5:45                 ` Michal Hocko
2020-09-18 15:32                   ` Vijay Balakrishna
2020-09-21  7:00                     ` Michal Hocko
2020-09-15 18:22 ` Pavel Tatashin
2020-09-15 18:22   ` Pavel Tatashin

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