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[209.85.218.47]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b842a2338cbsm1302405766b.14.2026.01.09.21.33.58 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 09 Jan 2026 21:33:58 -0800 (PST) Received: by mail-ej1-f47.google.com with SMTP id a640c23a62f3a-b7a72874af1so887512466b.3 for ; Fri, 09 Jan 2026 21:33:58 -0800 (PST) X-Received: by 2002:a17:907:3e20:b0:b7a:1bde:1224 with SMTP id a640c23a62f3a-b84451adc45mr1025593866b.65.1768023237683; Fri, 09 Jan 2026 21:33:57 -0800 (PST) MIME-Version: 1.0 References: <20260110040217.1927971-1-viro@zeniv.linux.org.uk> In-Reply-To: <20260110040217.1927971-1-viro@zeniv.linux.org.uk> From: Linus Torvalds Date: Fri, 9 Jan 2026 19:33:41 -1000 X-Gmail-Original-Message-ID: X-Gm-Features: AZwV_Qj8IjwLAZBCGylKcDX863bYH6zw4Q89VsNZ53a8fR2SwhwzXKAkrSSBlRw Message-ID: Subject: Re: [RFC PATCH 00/15] kmem_cache instances with static storage duration To: Al Viro Cc: linux-mm@kvack.org, Vlastimil Babka , Harry Yoo , linux-fsdevel@vger.kernel.org, Christian Brauner , Jan Kara , Mateusz Guzik , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 5AC4B20005 X-Rspam-User: X-Stat-Signature: x8razh8u9obwdud7frd5qygi9ftz3e5x X-HE-Tag: 1768023241-383787 X-HE-Meta: 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 bQA7vQZf 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 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, 9 Jan 2026 at 18:01, Al Viro wrote: > > There's an alternative approach applicable at least to the caches > that are never destroyed, which covers a lot of them. No matter what, > runtime_const for pointers is not going to be faster than plain &, > so if we had struct kmem_cache instances with static storage duration, we > would be at least no worse off than we are with runtime_const variants. I like it. Much better than runtime_const for these things. That said, I don't love the commit messages. "turn xyzzy static-duration" reads very oddly to me, and because I saw the emails out of order originally it just made me go "whaa?" So can we please explain this some more obvious way. Maybe just "Make xyz be statically allocated". Yes, I'm nitpicking, but I feel like explaining core patches is worth the effort. And maybe that's for the sad reason that I read more explanations than code these days '/ Linus