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Mon, 16 Jun 2025 16:49:49 -0700 (PDT) MIME-Version: 1.0 References: <57e110be6d8387e403b4ef1f3b10714c36afbb51.1750040317.git.gehao@kylinos.cn> In-Reply-To: From: Suren Baghdasaryan Date: Mon, 16 Jun 2025 16:49:38 -0700 X-Gm-Features: AX0GCFuAg0WOrYYwGLiRGPPUQaw6f_v9xmxf5R_loH7rX4qxsikqGy9OZp4O2vA Message-ID: Subject: Re: [PATCH v3 1/2] mm: Optimize the ARCH_NEEDS_WEAK_PER_CPU logic for s390/alpha architectures To: Mike Rapoport Cc: David Hildenbrand , Hao Ge , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Richard Henderson , Matt Turner , Dennis Zhou , Tejun Heo , Christoph Lameter , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Kent Overstreet , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, linux-s390@vger.kernel.org, Hao Ge Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 1AABE40006 X-Rspamd-Server: rspam03 X-Rspam-User: X-Stat-Signature: gow8g5cukocx86o65craj6zkkdqcgd1f X-HE-Tag: 1750117790-564011 X-HE-Meta: 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 w/hAeiii qy0dSvO1j3jjIetX+QTV7+LXE1RlWjctTfYEPQ7S5CTKq7OsF+3Ge4yX5CAUrdCrWfQ0gpxx59Tf4vpY4e2E34bXcqozyenpYbYI3cuziHSDx11ywHSpTCRMByig1Fda6WxLATecy1h7jEv2DlLl78M9R37aSL501zLq9KJIRvx7SmFAcvP0JdbEAFvLOnWpD7nBX4qgJx3u+dAsvGkQosDgJGtPQniJxmFbdL41m17LNxi0Lfe8fQkzCqc+Yo2Ijq46ztGuEzsUTzms= 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 Mon, Jun 16, 2025 at 1:55=E2=80=AFAM Mike Rapoport wro= te: > > On Mon, Jun 16, 2025 at 09:59:09AM +0200, David Hildenbrand wrote: > > On 16.06.25 04:29, Hao Ge wrote: > > > From: Hao Ge > > > > subject is misleading: we are not optimizing anything in this patch, do= we? > > > > It should probably be called > > > > "mm/percpu: rename ARCH_NEEDS_WEAK_PER_CPU to MODULE_NEED_WEAK_PER_CPU"= or > > sth. like that. > > > > > > > Add the ARCH_NEEDS_WEAK_PER_CPU option to the mm Kconfig file > > > and enable it for the s390 and alpha architectures. > > > And replace all instances of ARCH_NEEDS_WEAK_PER_CPU > > > in the kernel code with MODULE_NEEDS_WEAK_PER_CPU. > > > > Most of the description here should likely go to patch #2. See below. > > ... > > > So what you could do is move the actual introduction of > > CONFIG_ARCH_NEEDS_WEAK_PER_CPU to patch #2, where it is actually used, = and > > limit this patch to the rename. > > > > Similarly, teak the patch description to reflect only that. > > Right, if the patch only renames ARCH_NEEDS_WEAK_PER_CPU to > MODULE_NEEDS_WEAK_PER_CPU the description can be as simple as > > mm/percpu: rename ARCH_NEEDS_WEAK_PER_CPU to MODULE_NEEDS_WEAK_PER_CPU > > as a preparation for introduction of CONFIG_ARCH_NEEDS_WEAK_PER_CPU. > No functional changes. Yeah, the title is misleading and the description is too complicated. Mike's suggested title sounds better to me and for description I would say something like: ARCH_NEEDS_WEAK_PER_CPU is currently defined only for modules and therefore fails to represent requirements of the architecture. This prevents us using it for conditions which are applicable when building both modules and the kernel. To handle such conditions, make it a Kconfig option and add MODULE_NEEDS_WEAK_PER_CPU for the cases when the condition applies only to modules. And now that I'm looking at the change I realize that we probably don't even need a separate MODULE_NEEDS_WEAK_PER_CPU. It will be used only in one place and can be replaced with: #if defined(CONFIG_ARCH_NEEDS_WEAK_PER_CPU) && defined(MODULE) The code inside arch/{alpha|s390}/include/asm/percpu.h that defines MODULE_NEEDS_WEAK_PER_CPU can be completely removed and in arch/alpha/Kconfig you can have: select ARCH_NEEDS_WEAK_PER_CPU if CONFIG_SMP to preserve CONFIG_SMP dependency. That seems to me like a nicer cleanup. > > > -- > > Cheers, > > > > David / dhildenb > > > > -- > Sincerely yours, > Mike.