Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 31 Aug 2023 13:29:24 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     David Hildenbrand <david@redhat.com>
Cc:     "Huang, Ying" <ying.huang@intel.com>,
        Ryan Roberts <ryan.roberts@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Yin Fengwei <fengwei.yin@intel.com>,
        Yu Zhao <yuzhao@google.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        Yang Shi <shy828301@gmail.com>, Zi Yan <ziy@nvidia.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Itaru Kitayama <itaru.kitayama@gmail.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v5 3/5] mm: LARGE_ANON_FOLIO for improved performance
Message-ID: <ZPCHpOtYgq32leay@casper.infradead.org>
References: <20230810142942.3169679-1-ryan.roberts@arm.com>
 <20230810142942.3169679-4-ryan.roberts@arm.com>
 <87v8dg6lfu.fsf@yhuang6-desk2.ccr.corp.intel.com>
 <5c9ba378-2920-4892-bdf0-174e47d528b7@arm.com>
 <87cyz43s63.fsf@yhuang6-desk2.ccr.corp.intel.com>
 <4e14730b-4e4c-de30-04bb-9f3ec4a93754@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <4e14730b-4e4c-de30-04bb-9f3ec4a93754@redhat.com>
Precedence: bulk

On Thu, Aug 31, 2023 at 09:57:46AM +0200, David Hildenbrand wrote:
> As raised in another mail, we can then discuss
> * how we want to call this feature (transparent large pages? there is
>   the concern that "THP" might confuse users. Maybe we can consider
>   "large" the more generic version and "huge" only PMD-size, TBD)
> * how to expose it in stats towards the user (e.g., /proc/meminfo)
> * which minimal toggles we want
> 
> I think there *really* has to be a way to disable it for a running system,
> otherwise no distro will dare pulling it in, even after we figured out the
> other stuff.
> 
> Note that for the pagecache, large folios can be disabled and distributions
> are actively making use of that.

You can't.  Well, you can for shmem/tmpfs, but you have to edit the
source code or disable CONFIG_TRANSPARENT_HUGEPAGE to disable it for XFS.