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.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6CAD5C433F5 for ; Wed, 20 Oct 2021 14:12:07 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 19EC960EB2 for ; Wed, 20 Oct 2021 14:12:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 19EC960EB2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id A20096B0071; Wed, 20 Oct 2021 10:12:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9CCA86B0072; Wed, 20 Oct 2021 10:12:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8BCC7900002; Wed, 20 Oct 2021 10:12:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0211.hostedemail.com [216.40.44.211]) by kanga.kvack.org (Postfix) with ESMTP id 7E1106B0071 for ; Wed, 20 Oct 2021 10:12:06 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 31539180EAE33 for ; Wed, 20 Oct 2021 14:12:06 +0000 (UTC) X-FDA: 78717005052.28.319041B Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf19.hostedemail.com (Postfix) with ESMTP id EBD37B0000B2 for ; Wed, 20 Oct 2021 14:12:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=KRTYJRPRYXm9ZqJy2lw2hJUmwgSE6jOOWBjg81sbw4s=; b=nkMjLC8wVsQezunuXjfT408tBj kH18as1wq/LCEf+14wdzpwtwaanEW7VgIagT4snLfmL9jsIeBSLB6HmtXrrZ0PBwPdHpBZxTfhbK5 iIZomUoy2oLAtrvT5cT44eK+TVkQxZaNZnDDHpLqkqNUrFiDTZ+pODYjioxewujb1GZrwhbu3P6B/ L2ZZZASPiHNRULrYXNiduTXcwtqwO7IjyxvbCCanossohZXivpFbqsqUVFjL2lvOYnWw2AoT4doUw UN58roeFyvFRetjQLgg/NsKfJKSwJQ2fx0KgcCNhI0tRuok/uvbRht/QHnwyH/5YTThJrzpOON2/g lPTlZZXw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mdCFr-00CYGK-Nl; Wed, 20 Oct 2021 14:08:03 +0000 Date: Wed, 20 Oct 2021 15:07:43 +0100 From: Matthew Wilcox To: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: linux-kernel@vger.kernel.org, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Vlastimil Babka , linux-mm@kvack.org, Dave Taht Subject: Re: [RFC PATCH] mm, slob: Rewrite SLOB using segregated free list Message-ID: References: <20211020135535.517236-1-42.hyeyoo@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211020135535.517236-1-42.hyeyoo@gmail.com> Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=nkMjLC8w; dmarc=none; spf=none (imf19.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: EBD37B0000B2 X-Stat-Signature: 9oczwohz3fp91i5o1wgewjfyxukiq8xy X-HE-Tag: 1634739122-814538 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, Oct 20, 2021 at 01:55:35PM +0000, Hyeonggon Yoo wrote: > Hello linux-mm, I rewrote SLOB using segregated free list, > to understand SLOB and SLUB more. It uses more kilobytes > of memory (48kB on 32bit tinyconfig) and became 9~10x faster. > > But after rewriting, I thought I need to discuss what SLOB is for. > According to Matthew, SLOB is for small machines whose > memory is 1~16 MB. > > I wonder adding 48kB on SLOB memory for speed/lower latency > is worth or harmful. > > So.. questions in my head now: > - Who is users of SLOB? > - Is it harmful to add some kilobytes of memory into SLOB? > - Is it really possible to run linux under 10MB of RAM? > (I failed with tinyconfig.) > - What is the boundary to make decision between SLOB and SLUB? There certainly are people running Linux on such small machines. Nicolas Pitre talked about what it takes to do it in a series of four articles: https://lwn.net/Articles/746780/ It's been a couple of decades since I was last paid to work on such a system. Dave Taht (cc'd) may be able to help you find people who care about these use cases. And maybe they can tell you whether 9-10x faster for 48kB extra memory consumption is a good tradeoff for them.