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[109.81.88.120]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-aa5996df797sm615573366b.68.2024.12.03.04.06.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Dec 2024 04:06:57 -0800 (PST) Date: Tue, 3 Dec 2024 13:06:56 +0100 From: Michal Hocko To: Frank van der Linden Cc: Mateusz Guzik , linux-mm@kvack.org, akpm@linux-foundation.org, Muchun Song , Miaohe Lin , Oscar Salvador , David Hildenbrand , Peter Xu , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/hugetlb: optionally pre-zero hugetlb pages Message-ID: References: <20241202202058.3249628-1-fvdl@google.com> <3tqmyo3qqaykszxmrmkaa3fo5hndc4ok6xrxozjvlmq5qjv4cs@2geqqedyfzcf> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: F08AAA0029 X-Stat-Signature: cjo9tnxyrhmrupynh6yxxxj67j5gau8f X-Rspam-User: X-HE-Tag: 1733227605-460259 X-HE-Meta: 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 7ZxFcV7J 7B5NYemSktT+FdHwvIwj+wKOAbXkVv8tgwRRztRd39X1PlpHKPwMetvdBI/yjKGfWu5Z6Pa2SN4z3R/agEjWd5UWRLApZWUjF5SXDA5tmWK+ItchperypBSG53OXr7UGSiDe8DhTVevM+q1Bc0mPqpp04oSfzGdg/Okb1A760b9HHFSWxqujb0nTZcm+V5TG9mrlpyJKFLF3QWeC2rHO8JfYosaW9aZ2Kh3ytpZICLE2BCLgNnvsubyxLRGQvCyQgdSK52mAZLFjQrqNsBUqP4JX6l92RCjCpNmbC3oqbGuAhhMH8cq+glsMr8/+/WqZX3bIlzcYHObbgBJ56yspEi/8Z+kLpLQefgp1R X-Bogosity: Ham, tests=bogofilter, spamicity=0.000004, 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 Mon 02-12-24 14:50:49, Frank van der Linden wrote: > On Mon, Dec 2, 2024 at 1:58 PM Mateusz Guzik wrote: > > Any games with "background zeroing" are notoriously crappy and I would > > argue one should exhaust other avenues before going there -- at the end > > of the day the cost of zeroing will have to get paid. > > I understand that the concept of background prezeroing has been, and > will be, met with some resistance. But, do you have any specific > concerns with the patch I posted? It's pretty well isolated from the > rest of the code, and optional. The biggest concern I have is that the overhead is payed by everybody on the system - it is considered to be a system overhead regardless only part of the workload benefits from hugetlb pages. In other words the workload using those pages is not accounted for the use completely. If the startup latency is a real problem is there a way to workaround that in the userspace by preallocating hugetlb pages ahead of time before those VMs are launched and hand over already pre-allocated pages? -- Michal Hocko SUSE Labs