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[209.85.219.172]) by smtp.gmail.com with ESMTPSA id o9-20020a05622a138900b003a582090530sm8582045qtk.83.2022.11.09.08.45.44 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Nov 2022 08:45:46 -0800 (PST) Received: by mail-yb1-f172.google.com with SMTP id 63so21670810ybq.4 for ; Wed, 09 Nov 2022 08:45:44 -0800 (PST) X-Received: by 2002:a05:6902:503:b0:6cf:c510:6a23 with SMTP id x3-20020a056902050300b006cfc5106a23mr40745720ybs.380.1668012343710; Wed, 09 Nov 2022 08:45:43 -0800 (PST) MIME-Version: 1.0 References: <87187c52-ae48-130b-6479-ae1023915bc1@suse.cz> <20221109155008.GC307514@darkstar.musicnaut.iki.fi> In-Reply-To: <20221109155008.GC307514@darkstar.musicnaut.iki.fi> From: Geert Uytterhoeven Date: Wed, 9 Nov 2022 17:45:32 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: Deprecating and removing SLOB To: Aaro Koskinen Cc: Vlastimil Babka , Pasha Tatashin , Christoph Lameter , David Rientjes , Joonsoo Kim , Pekka Enberg , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Matthew Wilcox , Roman Gushchin , Linus Torvalds , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Catalin Marinas , Rustam Kovhaev , Andrew Morton , Josh Triplett , Arnd Bergmann , Russell King , Alexander Shiyan , Janusz Krzysztofik , Tony Lindgren , Yoshinori Sato , Rich Felker , Jonas Bonn , Stefan Kristiansson , Stafford Horne , "linux-arm-kernel@lists.infradead.org" , openrisc@lists.librecores.org, linux-riscv@lists.infradead.org, linux-sh@vger.kernel.org Content-Type: text/plain; charset="UTF-8" ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668012350; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Ews1zWN1f/PR7HGzfMn+lenNKSw7QezbzurfTC9dGEg=; b=oCS9hbzo+okDYd412lgnkq5Mqtz5M+KLcuITDDqsCE5ETRTPitiQRkulw1dGxM5bIVGd+f q9tdjm2SzCz3Q/X5FKuQPqeRiM3AjKUSyQhTc9mxqR0XceJXLMaYPTGItY2/EYS9/Z6LAX e/kT11B/kiLXvO/vYa2xQc9nSlfWeVQ= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf08.hostedemail.com: domain of geert.uytterhoeven@gmail.com designates 209.85.219.54 as permitted sender) smtp.mailfrom=geert.uytterhoeven@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1668012350; a=rsa-sha256; cv=none; b=nYRA7n2o4TLeICHGnXxcoihGzqcB6EJ3Jc/fbTCvESCO5k78VF7K1ITjj1xNDEgAYM0vxy ZKMwi2vPPTBMHDTcIa9q7ht6942F9YxbQ+42A9rvD0AN9Yp0DREU31GOY0qXhuvxvR3gBD C8UGjv2+e5JoVwK/tIuUGCUXMLD/Ktw= X-Rspamd-Queue-Id: 9F780160005 X-Rspam-User: X-Rspamd-Server: rspam08 Authentication-Results: imf08.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf08.hostedemail.com: domain of geert.uytterhoeven@gmail.com designates 209.85.219.54 as permitted sender) smtp.mailfrom=geert.uytterhoeven@gmail.com X-Stat-Signature: 1bpiikdz638mapiqonjwdpskwoqi5cci X-HE-Tag: 1668012350-716321 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: On Wed, Nov 9, 2022 at 4:53 PM Aaro Koskinen wrote: > On Wed, Nov 09, 2022 at 10:00:25AM +0100, Vlastimil Babka wrote: > > > On Tue, Nov 8, 2022 at 10:55 AM Vlastimil Babka wrote: > > >> I believe SLOB can be removed because: > > >> > > >> - AFAIK nobody really uses it? It strives for minimal memory footprint > > >> by putting all objects together, which has its CPU performance costs > > >> (locking, lack of percpu caching, searching for free space...). I'm not > > >> aware of any "tiny linux" deployment that opts for this. For example, > > >> OpenWRT seems to use SLUB and the devices these days have e.g. 128MB > > >> RAM, not up to 16 MB anymore. I've heard anecdotes that the performance > > >> SLOB impact is too much for those who tried. Googling for > > >> "CONFIG_SLOB=y" yielded nothing useful. > > > > > > I am all for removing SLOB. > > > > > > There are some devices with configs where SLOB is enabled by default. > > > Perhaps, the owners/maintainers of those devices/configs should be > > > included into this thread: > > [...] > > > > arch/arm/configs/omap1_defconfig:CONFIG_SLOB=y > > I have been using SLUB on my OMAP1 boards with 32 MB RAM, because of > better debugging features and the memory footprint difference doesn't > really matter for my use cases. Looking at history why SLOB was added > there, it seems it came from 6cfce27c14aa ("omap1: Add omap1_defconfig") > when separate boards configs were merged, and SX1 board happened to have > SLOB in there. This board is nowadays only used in QEMU anyway. > > There are OMAP1 boards with only 16 MB, but support for those boards > will be removed. So from OMAP1 side, I don't think there is any real > need for SLOB anymore. Interestingly, the m68k defconfigs use either SLAB, or the default (SLUB). So the poor old m68k machines (many of which have less than 32 MiB) seem to do fine without SLOB... Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds