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Date:   Fri, 23 Oct 2020 10:49:56 +0200
From:   Michal Hocko <mhocko@suse.com>
To:     Rik van Riel <riel@surriel.com>
Cc:     Hugh Dickins <hughd@google.com>, Yu Xu <xuyu@linux.alibaba.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@suse.de>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        linux-mm@kvack.org, kernel-team@fb.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm,thp,shmem: limit shmem THP alloc gfp_mask
Message-ID: <20201023084956.GS23790@dhcp22.suse.cz>
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On Thu 22-10-20 23:40:53, Rik van Riel wrote:
> On Thu, 2020-10-22 at 19:54 -0700, Hugh Dickins wrote:
[...]
> > But it's likely that they have accumulated some defrag wisdom, which
> > tmpfs can take on board - but please accept that in using a huge
> > mount,
> > the preference for huge has already been expressed, so I don't expect
> > anon THP alloc_hugepage_direct_gfpmask() choices will map one to one.
> 
> In my mind, the huge= mount options for tmpfs corresponded
> to the "enabled" anon THP options, denoting a desired end
> state, not necessarily how much we will stall allocations
> to get there immediately.

It is really unfortunate that our configuration space is so huge and
messy but we have to live with that now.

Anyway, I would tend to agree that with an absense of per-mount defrag
configuration it makes sense to use the global one. Is anybody aware of
usecases where a mount specific configuration would make sense?
-- 
Michal Hocko
SUSE Labs