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Tue, 26 Aug 2025 05:03:49 -0700 (PDT) MIME-Version: 1.0 References: <20250826071948.2618-1-laoar.shao@gmail.com> In-Reply-To: From: Yafang Shao Date: Tue, 26 Aug 2025 20:03:13 +0800 X-Gm-Features: Ac12FXxAMWmgXqxqMn86i1pgaDl2fr9t1rbnFdtwuYwKZ28ngZsdmxMlz2l-U7E Message-ID: Subject: Re: [PATCH v6 mm-new 00/10] mm, bpf: BPF based THP order selection To: David Hildenbrand Cc: akpm@linux-foundation.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, hannes@cmpxchg.org, usamaarif642@gmail.com, gutierrez.asier@huawei-partners.com, willy@infradead.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, ameryhung@gmail.com, rientjes@google.com, corbet@lwn.net, bpf@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, yu c chen , =?UTF-8?Q?Michal_Koutn=C3=BD?= , libo.chen@oracle.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 17D2E1C0005 X-Stat-Signature: gj7eoj1a1bot6oas16xxgm6pmir5tcm8 X-Rspam-User: X-HE-Tag: 1756209830-955772 X-HE-Meta: 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 SA7PrxW6 L2ocJ9ZAzdtlgn6wme0cspvEK7nB1NG7ru3EWdrXbfUoNxX8= 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, Aug 26, 2025 at 3:42=E2=80=AFPM David Hildenbrand wrote: > > On 26.08.25 09:19, Yafang Shao wrote: > > Background > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > > > Our production servers consistently configure THP to "never" due to > > historical incidents caused by its behavior. Key issues include: > > - Increased Memory Consumption > > THP significantly raises overall memory usage, reducing available me= mory > > for workloads. > > > > - Latency Spikes > > Random latency spikes occur due to frequent memory compaction trigge= red > > by THP. > > > > - Lack of Fine-Grained Control > > THP tuning is globally configured, making it unsuitable for containe= rized > > environments. When multiple workloads share a host, enabling THP wit= hout > > per-workload control leads to unpredictable behavior. > > > > Due to these issues, administrators avoid switching to madvise or alway= s > > modes=E2=80=94unless per-workload THP control is implemented. > > > > To address this, we propose BPF-based THP policy for flexible adjustmen= t. > > Additionally, as David mentioned [0], this mechanism can also serve as = a > > policy prototyping tool (test policies via BPF before upstreaming them)= . > > There is a lot going on and most reviewers (including me) are fairly > busy right now, so getting more detailed review could take a while. > > This topic sounds like a good candidate for the bi-weekly MM alignment > session. > > Would you be interested in presenting the current bpf interface, how to > use it, drawbacks, todos, ... in that forum? Sure. > > David Rientjes, who organizes this meeting, is already on Cc. DavidR had previously reached out to me about this patchset. Hello DavidR, Would September 17 from 9:00=E2=80=9310:00 AM PDT (UTC-7) work for discussi= ng this topic? If that time isn=E2=80=99t convenient, I=E2=80=99m happy to sch= edule a later session=E2=80=94this will also give me some time to prepare a brief slide. On a related note, I=E2=80=99d like to take this opportunity to also share = a short proposal on BPF-based NUMA balancing. On our AMD EPYC servers, many services experience significant performance degradation due to cross-NUMA access. While NUMA balancing can help mitigate this, its current global enable/disable implementation often leads to overall system performance regression. We are exploring the use of BPF to selectively enable NUMA balancing only for NUMA-sensitive services, thereby minimizing unintended side effects. A similar approach has been proposed in [0] using prctl() or a cgroup interface. We believe this use case is particularly well-suited for a BPF-based solution, and I=E2=80=99ll briefly outline why = in the slide. I=E2=80=99ve included the developers from [0] in CC for visibili= ty, in case they are interested in joining the discussion. Looking forward to your thoughts. [0]. https://lore.kernel.org/lkml/20250625102337.3128193-1-yu.c.chen@intel.= com/ --=20 Regards Yafang