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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 32B5BC00140 for ; Tue, 2 Aug 2022 12:19:19 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BA8988E0001; Tue, 2 Aug 2022 08:19:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B585A6B0072; Tue, 2 Aug 2022 08:19:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A48A58E0001; Tue, 2 Aug 2022 08:19:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 977826B0071 for ; Tue, 2 Aug 2022 08:19:18 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 69ABD1C6C29 for ; Tue, 2 Aug 2022 12:19:18 +0000 (UTC) X-FDA: 79754557596.21.C412486 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf07.hostedemail.com (Postfix) with ESMTP id 0FB05400FE for ; Tue, 2 Aug 2022 12:19:16 +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=d91QpCRfxx5Y4MrRAzxfHYk7Hf+lfOmM6s3JhedqiyY=; b=XdBVqbfOGO1g4zmZJVepZ+18kW ftQ9NjDsBYd2VjA1nWZh6e9r/HyuI29IGAqtz2ypbU0Cxm/S2ZoREkpQfEatzcqrK4JDudv5Dw8rd /tL3jXBSC7Zquhmo5bSToqO25dTGLycNzMwFvv9BZL5L3BqV1bxUxK/uUPzHBfUVOeF/EmgrjDMI3 EAjOzalIApw4mrCYKk4Cuw6gdG1kApMe6qObmEne1MtXXwBxK5OF6xuzPXlHIogLoDy2iYuncIABT b/Eb0JHC0xln00cGr9Zmz+VPzd6dv6D2GI+sV67zTM2vtualC5Sd5U27ReA4k25ghs0340XC02wgQ FnkFPLHw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1oIqre-008LCq-B4; Tue, 02 Aug 2022 12:19:10 +0000 Date: Tue, 2 Aug 2022 13:19:10 +0100 From: Matthew Wilcox To: "Yeleswarapu, Nagaradhesh" Cc: "Vlastimil Babka (SUSE)" , "linux-mm@kvack.org" Subject: Re: Regarding Virtual address split for a specific process Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=XdBVqbfO; spf=none (imf07.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1659442758; a=rsa-sha256; cv=none; b=X7pxluy09mcFUCVx33CDFyoNwugSH4QXNZgg3qDIzs1JouFVZcrcLPHb1RN0CoTun3h7oX bUAeTGm+U0+XDfhuKoblxXIpWek6KEGCktab42JWqTJMeI1dNeSPQvpPWslu83/0nezUJo UR3eGt+CV0118dicv2qVwxQfkcNwB98= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1659442758; 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:dkim-signature; bh=d91QpCRfxx5Y4MrRAzxfHYk7Hf+lfOmM6s3JhedqiyY=; b=rmGAFszvvyCUvg5vDIK1PCE+UAXkalz0U0TXMRwEzKRbxg7X28oh/EJEcT9VaJEM2Bni8e 3mFq3lKpUqyAIGt12+YOFK1DDXq5fOeOJ3XnCvkYzrnNuua9BRYJng0ePdMMF44+I8S+VH 2fKPuspYsDf0E6VuIgotIqoy5pD45/o= X-Stat-Signature: 56z9t5xzqn4ozwf5mapmrrcq18gd3zor X-Rspamd-Queue-Id: 0FB05400FE Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=XdBVqbfO; spf=none (imf07.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1659442756-405804 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, Aug 02, 2022 at 12:08:36PM +0000, Yeleswarapu, Nagaradhesh wrote: > [AMD Official Use Only - General] > > > On 8/1/22 08:45, Yeleswarapu, Nagaradhesh wrote: > > > [AMD Official Use Only - General] > > > > > > Hi, > > > > > > From the config options(CONFIG_VMSPLIT_3G/2G/1G), looks like 3/1 or 2/2 or > > 1/3 split is for all the user space processes. > > > > Yeah, but only for 32bit architectures. > Thanks for your response, can you please share details on how to change memory split for a 64bit architecture? You can't. With a 64-bit kernel, you either get 47 bits (128TB) of virtual address for a 64-bit process with 4-level page tables or 56 bits (64PB) with 64-bit kernels. I believe 32-bit tasks get almost 4GB of address space when run on a 64-bit kernel, but honestly I've forgotten. > > > > > Is it possible to do 2/2 split for a specific process and let all the other > > processes use default 3/1 (user/kernel) VA split? > > > > No, it's hardcoded in the kernel compilation. What would be the use case? > We are trying to offload a task from one Host to another Host, to achieve this we are looking to change > offload process Virtual address split to 2G/2G and let other processes use default memory split(3G/1G). 32-bit kernels are still relevant? They don't even get security fixes in some cases. https://lore.kernel.org/lkml/Ys%2FkfDk7mVE09N3L@worktop.programming.kicks-ass.net/