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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id 3f1490d57ef6-e842aaed6e4sm3886264276.20.2025.06.25.14.52.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Jun 2025 14:52:03 -0700 (PDT) Date: Wed, 25 Jun 2025 14:51:52 -0700 (PDT) From: Hugh Dickins To: David Hildenbrand cc: Lorenzo Stoakes , Hugh Dickins , Baolin Wang , akpm@linux-foundation.org, ziy@nvidia.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, zokeefe@google.com, shy828301@gmail.com, usamaarif642@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 0/2] fix MADV_COLLAPSE issue if THP settings are disabled In-Reply-To: <8691d74b-67ee-4e26-81ac-f6bf1725361e@redhat.com> Message-ID: <3ec483b4-9f13-daa4-68ac-2af3eabe8583@google.com> References: <75c02dbf-4189-958d-515e-fa80bb2187fc@google.com> <9cb94544-f65a-4394-b1e2-bfb226ead31c@redhat.com> <8691d74b-67ee-4e26-81ac-f6bf1725361e@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 570011A0006 X-Stat-Signature: 1txc6dmmnjsjmj3mmh6h6tgc5qhpu99q X-Rspam-User: X-HE-Tag: 1750888325-495338 X-HE-Meta: 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 TqYZAEkF 03iLdG5GROckaUryQgcw/YYhnCDvDs7SoGwAF6uSjpj5C53WnK7tfd9z10+NlXpA1WdoRpwP3OQJin29b7SGG6FOex91KxuU5k4F0UVKJ4OdaiJ2v3+wpVlAjftR10IqS5YHtySJQZ2vT3vfPfxs+XKSZeg3GcNIfKqtThr+yeqAxnuQc4YuV6mV8uKVSVB8JwkHBmANctnMFOOI60OX4OByFbeeHBu6JhVsK3KLvOfLVmVi4rs/vhXCFn/Mz8if6thIK4NlgykeZW77uwQ+DcwJpLLXvOgcS894Q7TZFgp002E6kd6orIWKu2ME1TolfKZryx56JexZKYmySTkGCMGLNaLy8xfHcb2buql0j8MZy1lT/fQLeuONABA25sITk1JVnZeUbXydpr7+Npu28+iy+xA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.003403, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 25 Jun 2025, David Hildenbrand wrote: > > I know, See my other mail, the problem is rather if there is no somebody > relying on never+MADV_COLLAPSE from doing the MADV_COLLAPSE-documented thing. > > It's a mess. > > (I have the suspicion that Hugh might know of such a user :) ) I've not yet read my way through this firestorm I've raised, but on this point: no, I don't know of such a user. You'll be suspecting that I know of some such use by Google: no, I haven't even investigated to see if that's the case; I think not, I think we're not neverers, but cannot check at the moment (and might have got in a muddle with the defrag options). I never(!) bothered to investigate that, because if Google does rely on this behaviour, it is very easy for Google to maintain its own variation from whatever is decided here (though management won't like me saying so). My concern is for everyone else who read the madvise MADV_COLLAPSE manpage. Hugh