linux-kernel - [QUESTIONS] THP allocation in NUMA fault migration path

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Message-ID: <aa34f38e-5e55-bdb2-133c-016b91245533@linux.alibaba.com>
Date:   Wed, 17 Apr 2019 21:15:41 -0700
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...e.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     YangShi <yang.shi@...ux.alibaba.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: [QUESTIONS] THP allocation in NUMA fault migration path

Hi folks,

I noticed that there might be new THP allocation in NUMA fault migration 
path (migrate_misplaced_transhuge_page()) even when THP is disabled (set 
to "never"). When THP is set to "never", there should be not any new THP 
allocation, but the migration path is kind of special. So I'm not quite 
sure if this is the expected behavior or not?

And, it looks this allocation disregards defrag setting too, is this 
expected behavior too?

Thanks,

Yang