From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.librecores.org (lists.librecores.org [88.198.125.70]) by smtp.lore.kernel.org (Postfix) with ESMTP id 52E97C4167B for ; Sun, 13 Nov 2022 06:49:25 +0000 (UTC) Received: from [172.31.1.100] (localhost.localdomain [127.0.0.1]) by mail.librecores.org (Postfix) with ESMTP id 4797F24243; Sun, 13 Nov 2022 07:49:22 +0100 (CET) Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by mail.librecores.org (Postfix) with ESMTPS id BAC1D24A1E for ; Fri, 11 Nov 2022 21:46:58 +0100 (CET) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id D0608B8260C; Fri, 11 Nov 2022 20:46:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16855C433D6; Fri, 11 Nov 2022 20:46:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668199616; bh=+aijmCyFee7qWFeNljZb8zYD5+XuzsnyGaxX9FEYxpk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=UnwFL8wuWkoZyhSHDqs67j/LsmCKgpcpww1g7jCaWZ36JihNBOGBStyV6m2p2YLp+ m2905fbVL3d+YYvg5Yw6+fM2rewxOIR0BXA5PJNQb7wbR7rut9I32ZzXzgtbxINfcn ywzelh60+IhLjCHgH9LQeBHlGFBz+Su/dtPQQ7KQ5eWGcMuTG6UyLYdWb1u1/m+WfT AWnvj4oYpVtx2Yi88aEsVMDJHNkhw4lVBU9k1Di7od31GKlIx8ow4kj7mjLq5dO6Vi ujvifadc6imBUFXqg2RbvXS48bE0aDe4bgAMQCOKMiv9+sqVG6Zl0x5Xv7jiRhT7w9 B9u+Kk/K+VpHw== Date: Fri, 11 Nov 2022 20:46:46 +0000 From: Conor Dooley To: Vlastimil Babka Subject: Re: Deprecating and removing SLOB Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Mailman-Approved-At: Sun, 13 Nov 2022 07:49:20 +0100 X-BeenThere: openrisc@lists.librecores.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: Discussion around the OpenRISC processor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Rich Felker , linux-sh@vger.kernel.org, Tony Lindgren , Catalin Marinas , Roman Gushchin , Paul Cercueil , "linux-mm@kvack.org" , Conor.Dooley@microchip.com, Hyeonggon Yoo <42.hyeyoo@gmail.com>, Christoph Lameter , linux-riscv@lists.infradead.org, Jonas Bonn , Yoshinori Sato , Aaro Koskinen , Damien Le Moal , Janusz Krzysztofik , Russell King , Matthew Wilcox , David Rientjes , Pasha Tatashin , Arnd Bergmann , Josh Triplett , openrisc@lists.librecores.org, Joonsoo Kim , "linux-arm-kernel@lists.infradead.org" , Alexander Shiyan , "linux-kernel@vger.kernel.org" , Rustam Kovhaev , Pekka Enberg , Andrew Morton , Linus Torvalds Errors-To: openrisc-bounces@lists.librecores.org Sender: "OpenRISC" On Fri, Nov 11, 2022 at 11:33:30AM +0100, Vlastimil Babka wrote: > On 11/8/22 22:44, Pasha Tatashin wrote: > > On Tue, Nov 8, 2022 at 10:55 AM Vlastimil Babka wrote: > >> > >> Hi, > >> > >> as we all know, we currently have three slab allocators. As we discussed > >> at LPC [1], it is my hope that one of these allocators has a future, and > >> two of them do not. > >> > >> The unsurprising reasons include code maintenance burden, other features > >> compatible with only a subset of allocators (or more effort spent on the > >> features), blocking API improvements (more on that below), and my > >> inability to pronounce SLAB and SLUB in a properly distinguishable way, > >> without resorting to spelling out the letters. > >> > >> I think (but may be proven wrong) that SLOB is the easier target of the > >> two to be removed, so I'd like to focus on it first. > >> > >> 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: > > > > tatashin@soleen:~/x/linux$ git grep SLOB=y > > arch/riscv/configs/nommu_k210_defconfig:CONFIG_SLOB=y > > arch/riscv/configs/nommu_k210_sdcard_defconfig:CONFIG_SLOB=y > > arch/riscv/configs/nommu_virt_defconfig:CONFIG_SLOB=y > > Turns out that since SLOB depends on EXPERT, many of those lack it so > running make defconfig ends up with SLUB anyway, unless I miss something. > Only a subset has both SLOB and EXPERT: > > > git grep CONFIG_EXPERT `git grep -l "CONFIG_SLOB=y"` > arch/riscv/configs/nommu_virt_defconfig:CONFIG_EXPERT=y I suppose there's not really a concern with the virt defconfig, but I did check the output of `make nommu_k210_defconfig" and despite not having expert it seems to end up CONFIG_SLOB=y in the generated .config. I do have a board with a k210 so I checked with s/SLOB/SLUB and it still boots etc, but I have no workloads or w/e to run on it.