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([2a02:6b6f:e750:f900:146f:2c4f:d96e:4241]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-447f18251c7sm62768305e9.3.2025.05.21.02.31.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 21 May 2025 02:31:46 -0700 (PDT) Message-ID: Date: Wed, 21 May 2025 10:31:45 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 0/7] prctl: introduce PR_SET/GET_THP_POLICY To: "Liam R. Howlett" , Andrew Morton , david@redhat.com, linux-mm@kvack.org, hannes@cmpxchg.org, shakeel.butt@linux.dev, riel@surriel.com, ziy@nvidia.com, laoar.shao@gmail.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, npache@redhat.com, ryan.roberts@arm.com, vbabka@suse.cz, jannh@google.com, Arnd Bergmann , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@meta.com References: <20250519223307.3601786-1-usamaarif642@gmail.com> Content-Language: en-US From: Usama Arif In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4CE0B1C0004 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: nff3nbuhscqp96xmpkrdan76p3xxsonu X-HE-Tag: 1747819909-859989 X-HE-Meta: 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 mMffbLoG 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 21/05/2025 03:33, Liam R. Howlett wrote: > * Usama Arif [250519 18:34]: >> This series allows to change the THP policy of a process, according to the >> value set in arg2, all of which will be inherited during fork+exec: >> - PR_DEFAULT_MADV_HUGEPAGE: This will set VM_HUGEPAGE and clear VM_NOHUGEPAGE >> for the default VMA flags. It will also iterate through every VMA in the >> process and call hugepage_madvise on it, with MADV_HUGEPAGE policy. >> This effectively allows setting MADV_HUGEPAGE on the entire process. >> In an environment where different types of workloads are run on the >> same machine, this will allow workloads that benefit from always having >> hugepages to do so, without regressing those that don't. >> - PR_DEFAULT_MADV_NOHUGEPAGE: This will set VM_NOHUGEPAGE and clear VM_HUGEPAGE >> for the default VMA flags. It will also iterate through every VMA in the >> process and call hugepage_madvise on it, with MADV_NOHUGEPAGE policy. >> This effectively allows setting MADV_NOHUGEPAGE on the entire process. >> In an environment where different types of workloads are run on the >> same machine,this will allow workloads that benefit from having >> hugepages on an madvise basis only to do so, without regressing those >> that benefit from having hugepages always. >> - PR_THP_POLICY_SYSTEM: This will reset (clear) both VM_HUGEPAGE and >> VM_NOHUGEPAGE process for the default flags. >> > > Subject seems outdated now? PR_DEFAULT_ vs PR_SET/GET_THP ? No its not. prctl takes 5 args, the first 2 are relevant here. The first arg is to decide the op. This series introduces 2 ops. PR_SET_THP_POLICY and PR_GET_THP_POLICY to set and get the policy. This is the subject. The 2nd arg describes the policies: PR_DEFAULT_MADV_HUGEPAGE, PR_DEFAULT_MADV_NOHUGEPAGE and PR_THP_POLICY_SYSTEM. The subject is correct. > > On that note, doesn't it make sense to change the default mm flag under > PR_SET_MM? PR_SET_MM_FLAG maybe? I don't think thats the right approach. PR_SET_MM is used to modify kernel memory map descriptor fields. Thats not what we are doing here. I am not sure how the usecase in this series fits at all in the below switch statement for PR_SET_MM: switch (opt) { case PR_SET_MM_START_CODE: prctl_map.start_code = addr; break; case PR_SET_MM_END_CODE: prctl_map.end_code = addr; break; case PR_SET_MM_START_DATA: prctl_map.start_data = addr; break; case PR_SET_MM_END_DATA: prctl_map.end_data = addr; break; case PR_SET_MM_START_STACK: prctl_map.start_stack = addr; break; case PR_SET_MM_START_BRK: prctl_map.start_brk = addr; break; case PR_SET_MM_BRK: prctl_map.brk = addr; break; case PR_SET_MM_ARG_START: prctl_map.arg_start = addr; break; case PR_SET_MM_ARG_END: prctl_map.arg_end = addr; break; case PR_SET_MM_ENV_START: prctl_map.env_start = addr; break; case PR_SET_MM_ENV_END: prctl_map.env_end = addr; break; default: goto out; } > > Thanks, > Liam