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[80.187.83.110]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46fa9bf87c1sm27190025e9.3.2025.10.08.01.08.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Oct 2025 01:08:37 -0700 (PDT) Message-ID: <27e002e3-b39f-40f9-b095-52da0fbd0fc7@redhat.com> Date: Wed, 8 Oct 2025 10:08:33 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 mm-new 03/11] mm: thp: add support for BPF based THP order selection To: Alexei Starovoitov , Yafang Shao Cc: Andrew Morton , ziy@nvidia.com, baolin.wang@linux.alibaba.com, Lorenzo Stoakes , Liam Howlett , npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, Johannes Weiner , usamaarif642@gmail.com, gutierrez.asier@huawei-partners.com, Matthew Wilcox , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Amery Hung , David Rientjes , Jonathan Corbet , 21cnbao@gmail.com, Shakeel Butt , Tejun Heo , lance.yang@linux.dev, Randy Dunlap , bpf , linux-mm , "open list:DOCUMENTATION" , LKML References: <20250930055826.9810-1-laoar.shao@gmail.com> <20250930055826.9810-4-laoar.shao@gmail.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 03.10.25 04:18, Alexei Starovoitov wrote: > On Mon, Sep 29, 2025 at 10:59 PM Yafang Shao wrote: >> >> +unsigned long bpf_hook_thp_get_orders(struct vm_area_struct *vma, >> + enum tva_type type, >> + unsigned long orders) >> +{ >> + thp_order_fn_t *bpf_hook_thp_get_order; >> + int bpf_order; >> + >> + /* No BPF program is attached */ >> + if (!test_bit(TRANSPARENT_HUGEPAGE_BPF_ATTACHED, >> + &transparent_hugepage_flags)) >> + return orders; >> + >> + rcu_read_lock(); >> + bpf_hook_thp_get_order = rcu_dereference(bpf_thp.thp_get_order); >> + if (WARN_ON_ONCE(!bpf_hook_thp_get_order)) >> + goto out; >> + >> + bpf_order = bpf_hook_thp_get_order(vma, type, orders); >> + orders &= BIT(bpf_order); >> + >> +out: >> + rcu_read_unlock(); >> + return orders; >> +} > > I thought I explained it earlier. > Nack to a single global prog approach. I agree. We should have the option to either specify a policy globally, or more refined for cgroups/processes. It's an interesting question if a program would ever want to ship its own policy: I can see use cases for that. So I agree that we should make it more flexible right from the start. -- Cheers David / dhildenb