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 53767C433EF for ; Tue, 16 Nov 2021 19:42:05 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E903861B5E for ; Tue, 16 Nov 2021 19:42:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org E903861B5E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=pengaru.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 841786B006C; Tue, 16 Nov 2021 14:42:02 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 7F1516B0072; Tue, 16 Nov 2021 14:42:02 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6B8FD6B0073; Tue, 16 Nov 2021 14:42:02 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0082.hostedemail.com [216.40.44.82]) by kanga.kvack.org (Postfix) with ESMTP id 5B2B56B006C for ; Tue, 16 Nov 2021 14:42:02 -0500 (EST) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 0D4C5182CA120 for ; Tue, 16 Nov 2021 19:42:02 +0000 (UTC) X-FDA: 78815814084.29.438A079 Received: from shells.gnugeneration.com (shells.gnugeneration.com [66.240.222.126]) by imf03.hostedemail.com (Postfix) with ESMTP id D232E3006FBC for ; Tue, 16 Nov 2021 19:21:39 +0000 (UTC) Received: by shells.gnugeneration.com (Postfix, from userid 1000) id 468601A40175; Tue, 16 Nov 2021 11:21:48 -0800 (PST) Date: Tue, 16 Nov 2021 11:21:48 -0800 From: Vito Caputo To: Jens Axboe Cc: Matthew Wilcox , Andrew Morton , Ammar Faizi , Drew DeVault , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, io_uring Mailing List , Pavel Begunkov , linux-mm@kvack.org Subject: Re: [PATCH] Increase default MLOCK_LIMIT to 8 MiB Message-ID: <20211116192148.vjdlng7pesbgjs6b@shells.gnugeneration.com> References: <20211028080813.15966-1-sir@cmpwn.com> <593aea3b-e4a4-65ce-0eda-cb3885ff81cd@gnuweeb.org> <20211115203530.62ff33fdae14927b48ef6e5f@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: D232E3006FBC X-Stat-Signature: j5769pqawyjk4aycd8rttzp3xr45bx8e Authentication-Results: imf03.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf03.hostedemail.com: domain of swivel@shells.gnugeneration.com designates 66.240.222.126 as permitted sender) smtp.mailfrom=swivel@shells.gnugeneration.com X-HE-Tag: 1637090499-915468 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 Tue, Nov 16, 2021 at 11:55:41AM -0700, Jens Axboe wrote: > On 11/16/21 11:36 AM, Matthew Wilcox wrote: > > On Mon, Nov 15, 2021 at 08:35:30PM -0800, Andrew Morton wrote: > >> I'd also be interested in seeing feedback from the MM developers. > > [...] > >> Subject: Increase default MLOCK_LIMIT to 8 MiB > > > > On the one hand, processes can already allocate at least this much > > memory that is non-swappable, just by doing things like opening a lot of > > files (allocating struct file & fdtable), using a lot of address space > > (allocating page tables), so I don't have a problem with it per se. > > > > On the other hand, 64kB is available on anything larger than an IBM XT. > > Linux will still boot on machines with 4MB of RAM (eg routers). For > > someone with a machine with only, say, 32MB of memory, this allows a > > process to make a quarter of the memory unswappable, and maybe that's > > not a good idea. So perhaps this should scale over a certain range? > > > > Is 8MB a generally useful amount of memory for an iouring user anyway? > > If you're just playing with it, sure, but if you have, oh i don't know, > > a database, don't you want to pin the entire cache and allow IO to the > > whole thing? > > 8MB is plenty for most casual use cases, which is exactly the ones that > we want to "just work" without requiring weird system level > modifications to increase the memlock limit. > Considering a single fullscreen 32bpp 4K-resolution framebuffer is ~32MiB, I'm not convinced this is really correct in nearly 2022. If we're going to bump the default at the kernel, I'm with Matthew on making it autoscale within a sane range, depending on available memory. As an upper bound I'd probably look at the highest anticipated consumer resolutions, and handle a couple fullscreen 32bpp instances being pinned. Regards, Vito Caputo