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 D0EC1C4332F for ; Tue, 16 Nov 2021 19:46:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BA7C263215 for ; Tue, 16 Nov 2021 19:46:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240136AbhKPTtn (ORCPT ); Tue, 16 Nov 2021 14:49:43 -0500 Received: from shells.gnugeneration.com ([66.240.222.126]:48570 "EHLO shells.gnugeneration.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235941AbhKPTtm (ORCPT ); Tue, 16 Nov 2021 14:49:42 -0500 Received: by shells.gnugeneration.com (Postfix, from userid 1000) id AF72A1A40175; Tue, 16 Nov 2021 11:46:44 -0800 (PST) Date: Tue, 16 Nov 2021 11:46:44 -0800 From: Vito Caputo To: Drew DeVault Cc: Jens Axboe , Matthew Wilcox , Andrew Morton , Ammar Faizi , 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: <20211116194644.uyvfz4zzzjlbfqbm@shells.gnugeneration.com> References: <20211028080813.15966-1-sir@cmpwn.com> <593aea3b-e4a4-65ce-0eda-cb3885ff81cd@gnuweeb.org> <20211115203530.62ff33fdae14927b48ef6e5f@linux-foundation.org> <20211116192148.vjdlng7pesbgjs6b@shells.gnugeneration.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 16, 2021 at 08:25:33PM +0100, Drew DeVault wrote: > On Tue Nov 16, 2021 at 8:21 PM CET, Vito Caputo wrote: > > Considering a single fullscreen 32bpp 4K-resolution framebuffer is > > ~32MiB, I'm not convinced this is really correct in nearly 2022. > > Can you name a practical use-case where you'll be doing I/O with > uncompressed 4K framebuffers? The kind of I/O which is supported by > io_uring, to be specific, not, say, handing it off to libdrm. Obviously video/image editing software tends to operate on raw frames, and sometimes even persists them via filesystems. I haven't given it a lot of thought, but a framebuffer is a commonly used unit of memory allocation in code run on the CPU I've written over the years. Being able to pin those for something like io_uring (or some other DMA-possible interface) seems like an obvious memory-hungry thing to consider here if we're talking default upper bounds. Regards, Vito Caputo