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From: Vijay Balakrishna <vijayb@linux.microsoft.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Oleg Nesterov <oleg@redhat.com>, Song Liu <songliubraving@fb.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Pavel Tatashin <pasha.tatashin@soleen.com>,
	Allen Pais <apais@microsoft.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [v4] mm: khugepaged: avoid overriding min_free_kbytes set by user
Date: Thu, 17 Sep 2020 10:27:16 -0700	[thread overview]
Message-ID: <21c4788c-2516-2e47-5885-486c352c2b6e@linux.microsoft.com> (raw)
In-Reply-To: <20200917092805.GA29887@dhcp22.suse.cz>



On 9/17/2020 2:28 AM, Michal Hocko wrote:
> On Wed 16-09-20 23:39:39, Vijay Balakrishna wrote:
>> set_recommended_min_free_kbytes need to honor min_free_kbytes set by the
>> user.  Post start-of-day THP enable or memory hotplug operations can
>> lose user specified min_free_kbytes, in particular when it is higher than
>> calculated recommended value.
> 
> I was about to recommend a more detailed explanation when I have
> realized that this patch is not really needed after all. Unless I am
> missing something.
> 
> init_per_zone_wmark_min ignores the newly calculated min_free_kbytes if
> it is lower than user_min_free_kbytes. So calculated min_free_kbytes >=
> user_min_free_kbytes.
> 
> Except for value clamping when the value is reduced and this likely
> needs fixing. But set_recommended_min_free_kbytes should be fine.
> 

IIUC, after start-of-day if a user performs
- THP disable
- modifies min_free_bytes
- THP enable
above sequence currently wouldn't result in calling init_per_zone_wmark_min.

Thanks,
Vijay

  parent reply	other threads:[~2020-09-17 18:31 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-17  6:39 [v4] mm: khugepaged: avoid overriding min_free_kbytes set by user Vijay Balakrishna
2020-09-17  9:28 ` Michal Hocko
2020-09-17  9:34   ` Michal Hocko
2020-09-17 17:27   ` Vijay Balakrishna [this message]
2020-09-17 17:52     ` Michal Hocko
2020-09-17 18:16       ` Vijay Balakrishna
2020-09-18  5:56         ` Michal Hocko
2020-09-21 19:07           ` Vijay Balakrishna
2020-09-22  7:07             ` Kirill A. Shutemov
2020-09-22 10:07               ` Michal Hocko
2020-09-22 16:10                 ` Vijay Balakrishna

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