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Tue, 20 May 2025 21:28:46 -0700 (PDT) MIME-Version: 1.0 References: <20250520060504.20251-1-laoar.shao@gmail.com> <2345b8b9-b084-4661-8b55-61fd7fc7de57@lucifer.local> <82f7bca5-384f-41e5-a0fc-0e1e8e260607@gmail.com> In-Reply-To: From: Yafang Shao Date: Wed, 21 May 2025 12:28:09 +0800 X-Gm-Features: AX0GCFvEYBCpG5ieUqLgW7G-4T53eX0Vl0ZmrBW1VnRhKy_dwQL_lAIxVIqTVu4 Message-ID: Subject: Re: [RFC PATCH v2 0/5] mm, bpf: BPF based THP adjustment To: Matthew Wilcox Cc: Lorenzo Stoakes , Usama Arif , Nico Pache , akpm@linux-foundation.org, david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, hannes@cmpxchg.org, gutierrez.asier@huawei-partners.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, bpf@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 9E90840003 X-Rspamd-Server: rspam09 X-Stat-Signature: wetg8ta47dzdrr63nw7ks9jybm189mkw X-HE-Tag: 1747801727-589364 X-HE-Meta: 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 YEvZZ/hi iZK3D4cK1wFbuoLEIiROchLPLlwPxumE0JT/5NJpYoNokG1mdEkuQoVH1svOxcz9mvv62pcR8vfY5TFeFHP9UKS2xS2EFVla6/zXISfMf62Msv6u5v/I/EWRLKTcXMqIIoBHy1vd82BZC98UU/+XYvDzuZZP8piKOaCFne1nJM82SgD4TcumvApn5SUZ7BgWfIU9vM2vefEufWrdwUZcGDg8xQef498z0H9QPdjBOQfzmX/COzFq1xS2JSvqkiypom192hJ4Hs3sHOhqEp/PnQaLQEzsCz6eqavUDWi4meufOsv6VCiJGkdnKMhPOwSJv8VCUB37MvnmyZh1jNA5T5TZk5j+o9Lr1Wn+rUA51hBh+EeH22oLdNgh5Pxz77bnjY4NJbZokC/yaBee4ODCxqold2z3iw/R9bXHY 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 Tue, May 20, 2025 at 10:43=E2=80=AFPM Matthew Wilcox wrote: > > On Tue, May 20, 2025 at 03:35:49PM +0100, Lorenzo Stoakes wrote: > > I agree global settings are not fine-grained enough, but 'sys admins re= fuse > > to do X so we want to ignore what they do' is... really not right at al= l. > > Oh, we do that all the time, Leave the interface around but document > it's now a no-op. For example, file-backed memory ignores the THP > settings completely. This essentially invites downstream kernel developers to implement their own "file-enabled" solutions ;-) If you haven't yet encountered reports of file-backed THP causing performance regressions for specific workloads, you may be missing something. Our testing has confirmed performance degradation with certain HDFS workloads, even on the 6.12.y kernel - though I've prioritized discussing BPF-based THP control with you over investigating those specific cases. > And mounting an NFS filesystem as "intr" has > been a no-op for over a decade. --=20 Regards Yafang