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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 15D39C10DCE for ; Tue, 10 Mar 2020 20:15:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B8A2D222C3 for ; Tue, 10 Mar 2020 20:15:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727317AbgCJUPX (ORCPT ); Tue, 10 Mar 2020 16:15:23 -0400 Received: from shelob.surriel.com ([96.67.55.147]:50416 "EHLO shelob.surriel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726545AbgCJUPX (ORCPT ); Tue, 10 Mar 2020 16:15:23 -0400 Received: from imladris.surriel.com ([96.67.55.152]) by shelob.surriel.com with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.3) (envelope-from ) id 1jBlHa-0001Mz-JN; Tue, 10 Mar 2020 16:15:18 -0400 Message-ID: <4147bc1d429a4336dcb45a6cb2657d082f35ab25.camel@surriel.com> Subject: Re: [PATCH v2] mm: hugetlb: optionally allocate gigantic hugepages using cma From: Rik van Riel To: Mike Kravetz , Michal Hocko , Roman Gushchin Cc: Andrew Morton , Johannes Weiner , linux-mm@kvack.org, kernel-team@fb.com, linux-kernel@vger.kernel.org Date: Tue, 10 Mar 2020 16:15:18 -0400 In-Reply-To: <57494a9c-5c24-20b6-0bda-dac8bbb6f731@oracle.com> References: <20200310002524.2291595-1-guro@fb.com> <5cfa9031-fc15-2bcc-adb9-9779285ef0f7@oracle.com> <20200310180558.GD85000@carbon.dhcp.thefacebook.com> <4b78a8a9-7b5a-eb62-acaa-2677e615bea1@oracle.com> <20200310191906.GA96999@carbon.dhcp.thefacebook.com> <20200310193622.GC8447@dhcp22.suse.cz> <43e2e8443288260aa305f39ba566f81bf065d010.camel@surriel.com> <57494a9c-5c24-20b6-0bda-dac8bbb6f731@oracle.com> Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-C3ENaGOY3Fk1eu6XYAt6" User-Agent: Evolution 3.34.3 (3.34.3-1.fc31) MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-C3ENaGOY3Fk1eu6XYAt6 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2020-03-10 at 13:11 -0700, Mike Kravetz wrote: > On 3/10/20 12:46 PM, Rik van Riel wrote: > >=20 > > How would that work for architectures that have multiple > > possible hugetlbfs gigantic page sizes, where the admin > > can allocate different numbers of differently sized pages > > after bootup? >=20 > For hugetlb page reservations at boot today, pairs specifying size > and > quantity are put on the command line. For example, > hugepagesz=3D2M hugepages=3D512 hugepagesz=3D1G hugepages=3D64 >=20 > We could do something similiar for CMA. > hugepagesz=3D512M hugepages_cma=3D256 hugepagesz=3D1G hugepages_cma=3D64 >=20 > That would make things much more complicated (implies separate CMA > reservations per size) and may be overkill for the first > implementation. >=20 > Perhaps we limit CMA reservations to one gigantic huge page > size. The > architectures would need to define the default and there could be a > command line option to override. Something like, > default_cmapagesz=3D analogous to today's default_hugepagesz=3D. Then > hugepages_cma=3D is only associated with that default gigantic huge > page > size. >=20 > The more I think about it, the more I like limiting CMA reservations > to > only one gigantic huge page size (per arch). Why, though? The cma_alloc function can return allocations of different sizes at the same time. There is no limitation in the underlying code that would stop a user from allocating hugepages of different sizes through sysfs. Allowing the system administrator to allocate a little extra memory for the CMA pool could also allow us to work around initial issues of compaction/migration failing to move some of the pages, while we play whack-a-mole with the last corner cases. --=20 All Rights Reversed. --=-C3ENaGOY3Fk1eu6XYAt6 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEEKR73pCCtJ5Xj3yADznnekoTE3oMFAl5n9VYACgkQznnekoTE 3oN42ggAnLgkVOVgm54Qtqfu1IihZSXHTfyMBPLFs4nCFUBBMpzt+QZJkCYXzGZW kUnRyYQcTPalw5uwdKeL97uWxvARnR04kx6qA7cvocvEC8Xw4EYPPH0RPKXXHG1f qRa9bpR+TvYckp/FmYiWME2oMD3S0wxXdXEUOsgnooOxCHJ7SScSdcx+06MgbVDh 49qboipysfbgTzuKFXmto/TxKWS/8LyRWaeAVwBnDyHn8XYfhsI9xa7xBsvnxAjI qacZRHqa+DcV8//wOPAp0YZ6fD86FQI42Dzqmm0l3N+k8wtXITh6SRdKo7ODUGQc h+B3ysCd32l+vOsITPwcvgiHRhbU7g== =IuCs -----END PGP SIGNATURE----- --=-C3ENaGOY3Fk1eu6XYAt6--