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charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 7284DC000D X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: i8d9hwwa8rfif3kroyfnyksdatibuu6n X-HE-Tag: 1757712720-424072 X-HE-Meta: U2FsdGVkX1+mxZVukocgNEYEu4N9Ve4euroDtwf1hZhx3+CkbCaOlSLmH0RCv4RyDOxnpXkXBA23ufPcubcFIo6fOArwCjZWYB0o/AYTdW2vOR7kzXPGBxnt73uw6jncEclyzSxb5xz1lWRwNAUkmnuHpgCuNbhwGydtjI6wwSbpKhMbiM6vcWmjUeToG5TUJJHutNzaHTRYI86YFiNGvmwut1bkNJoeH5oSSRF2heEHp6Xos6tu1zGaj0rjA78v2AnTVPbEmfBb0K5kg9fqRpzOZulpm2s4+uOywcrV1DQZ1Bw/ubKuOr9ej3ZdtCDOkOfgtkL47Uuukpq6loPBO31eV+LEqITcT59O55xU0l5dzWlQ2Ty5agOk63uKYEC4bQ0xQeoYHRsts4TiGrZ0cxb3LdRaN+XuJdq2xFeZc2w8EKy/qPg6lpEO7fjGSUjylNOIi1Fynf/rrcErwVnJgZNTGdPPEcLZUQ9ZjLt0lB0EviO6C1aWE9LDCZwtpM3QooDymL81j0hnMPLmm2/O2GKLboRICCUX508/veI+PeO5MXiX/2HEmvBpg6rEaQPW4Guanu3Sp8emwLAdF7ccHtEDbzdHdLC2+vJQaOfr2L6lODEcHepc7j8vKkiRh8Nr38J741QZwSHr6CWMSgdIWHXIVZGNQi6W2fPvh9ikjhzEtxfMPYsmYEeXnx2wE7MKsbuin3Jc2WwDihMGDjdpVDJO+6M+VbCj52+v/FvXZ1xn3FhXkWAz8eaZVdeBTcIFQQ+N5wa6BVfF4kybHN+prh16ugNqQTc5xBrHw44Y9AOziek83tE4fj38sbXmhoWnnjXEIQs7XYDqfeV+2lqa0cdCVe1B7q9CJvZ0+uifxhyI0Zp/HS3CY/ZhoOmt3QsHUBw9HloUWUE0m+1wRMeNBWRGIzuxjSn7QMd7rfHS1aXMM5GizUd6ngaH/vIYQzSVAuO3nPjg5f0SXM6Thsc 4Pd1eOJI iRnnZqVCFxHBkx6envmp50j/dT1IFLgW6h3EZq4yHgX1En6vbNyRYQB4K5wgz04bkD4z4Mo8/6Y2gpRfTHvZI0N2zu6wywsFoMIlqkg0q20WB/YuRL0NkUnA6nJlV4IQBQ85c7cxRyWg/8iy8GZ6SQBIC/e0lyzVN/VKN1Rt+mXbwqoDNIos9FbU6qIRpoycvb/+ChyZ3HBPEufjjlmGPWx/fvXizu03yo7ASLiLXe4+vSJiccI2SQmXBZYx05J6n74peKXGYLsfYYwV2DcJztVwH5MqPuM8yvP4U8op55qp2CXsTiVZqc2aufmFPEEHvCocYdbR/VvRRpgDWRZ0PdA/hBBm6ipXL+4wp8qYNV/dPfQDKzJe+NjOYszTt2ljgDriB0JvqRj3prP6uoCMtVbQF7sxjL0nvhWjW+o1dR1jmaeKNsn/3ekLeMuQE7FlPKsMTOLVCJXOxugrfQFrfPOq3EmyRpv3sYR3cVI6j3O8OU9k= 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 Fri, Sep 12, 2025 at 2:29=E2=80=AFPM Shakeel Butt wrote: > > On Fri, Sep 12, 2025 at 02:24:26PM -0700, Alexei Starovoitov wrote: > > On Fri, Sep 12, 2025 at 2:03=E2=80=AFPM Suren Baghdasaryan wrote: > > > > > > On Fri, Sep 12, 2025 at 12:27=E2=80=AFPM Shakeel Butt wrote: > > > > > > > > +Suren, Roman > > > > > > > > On Mon, Sep 08, 2025 at 06:00:06PM -0700, Alexei Starovoitov wrote: > > > > > From: Alexei Starovoitov > > > > > > > > > > Since the combination of valid upper bits in slab->obj_exts with > > > > > OBJEXTS_ALLOC_FAIL bit can never happen, > > > > > use OBJEXTS_ALLOC_FAIL =3D=3D (1ull << 0) as a magic sentinel > > > > > instead of (1ull << 2) to free up bit 2. > > > > > > > > > > Signed-off-by: Alexei Starovoitov > > > > > > > > Are we low on bits that we need to do this or is this good to have > > > > optimization but not required? > > > > > > That's a good question. After this change MEMCG_DATA_OBJEXTS and > > > OBJEXTS_ALLOC_FAIL will have the same value and they are used with th= e > > > same field (page->memcg_data and slab->obj_exts are aliases). Even if > > > page_memcg_data_flags can never be used for slab pages I think > > > overlapping these bits is not a good idea and creates additional > > > risks. Unless there is a good reason to do this I would advise agains= t > > > it. > > > > Completely disagree. You both missed the long discussion > > during v4. The other alternative was to increase alignment > > and waste memory. Saving the bit is obviously cleaner. > > The next patch is using the saved bit. > > I will check out that discussion and it would be good to summarize that > in the commit message. Disgaree. It's not a job of a small commit to summarize all options that were discussed on the list. That's what the cover letter is for and there there are links to all previous threads.