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=-6.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 2B297C433E0 for ; Tue, 2 Feb 2021 17:17:16 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B3FA464ECE for ; Tue, 2 Feb 2021 17:17:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B3FA464ECE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3146B6B0071; Tue, 2 Feb 2021 12:17:15 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2C4216B0073; Tue, 2 Feb 2021 12:17:15 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 18C8A6B0075; Tue, 2 Feb 2021 12:17:15 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0206.hostedemail.com [216.40.44.206]) by kanga.kvack.org (Postfix) with ESMTP id 0077F6B0071 for ; Tue, 2 Feb 2021 12:17:14 -0500 (EST) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id CBDD6362E for ; Tue, 2 Feb 2021 17:17:13 +0000 (UTC) X-FDA: 77773983546.03.EF2F38B Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf01.hostedemail.com (Postfix) with ESMTP id E436331E2CD9 for ; Tue, 2 Feb 2021 12:49:27 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 4EEB964F45; Tue, 2 Feb 2021 12:49:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1612270167; bh=l1mxEt58DDcLUIYn/PeqqKhgepc/YzCCfJbWYo9gF+0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=m6OTQfqwmfzsDSuhaE02irM8RXZ+6I61yxWerp81AbIHaAEqJgnUU1Tago6YYG+PZ lr/J7OliC0mrwyFm+Yl+JHzEuSXK/3VdkUmPzprvLqNXJeT7c7s/R/J9ZCl2+IeFtF rRdT17MK63P20HXBjgkEetlpW86oX2ThKpxrHLgmDgGybcXOIhr5G1LeWie80VfNKg QlMcZq+bz+M1S4kZa3QSlb+JQ6x7L2zxJR92gCQJ28nKgn5G8407CWFGfDfkqlEtqc 0FuByC2cyuzV9p6QWIQuYAV6UBnFm4EyXxopzOj5OqjOkGbbBSYsX5rFiF13qam/3d 9vHDje5GpJPpg== Date: Tue, 2 Feb 2021 14:48:57 +0200 From: Mike Rapoport To: Michal Hocko Cc: James Bottomley , David Hildenbrand , Andrew Morton , Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , Elena Reshetova , "H. Peter Anvin" , Ingo Molnar , "Kirill A. Shutemov" , Matthew Wilcox , Mark Rutland , Mike Rapoport , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Rick Edgecombe , Roman Gushchin , Shakeel Butt , Shuah Khan , Thomas Gleixner , Tycho Andersen , Will Deacon , linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org, x86@kernel.org, Hagen Paul Pfeifer , Palmer Dabbelt Subject: Re: [PATCH v16 07/11] secretmem: use PMD-size pages to amortize direct map fragmentation Message-ID: <20210202124857.GN242749@kernel.org> References: <20210121122723.3446-8-rppt@kernel.org> <20210126114657.GL827@dhcp22.suse.cz> <303f348d-e494-e386-d1f5-14505b5da254@redhat.com> <20210126120823.GM827@dhcp22.suse.cz> <20210128092259.GB242749@kernel.org> <73738cda43236b5ac2714e228af362b67a712f5d.camel@linux.ibm.com> <6de6b9f9c2d28eecc494e7db6ffbedc262317e11.camel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: E436331E2CD9 X-Stat-Signature: fmjnyhf556o3tm4x3momtdjmpai6yn9j Received-SPF: none (kernel.org>: No applicable sender policy available) receiver=imf01; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1612270167-886199 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, Feb 02, 2021 at 10:35:05AM +0100, Michal Hocko wrote: > On Mon 01-02-21 08:56:19, James Bottomley wrote: > > I have also proposed potential ways out of this. Either the pool is not > fixed sized and you make it a regular unevictable memory (if direct map > fragmentation is not considered a major problem) I think that the direct map fragmentation is not a major problem, and the data we have confirms it, so I'd be more than happy to entirely drop the pool, allocate memory page by page and remove each page from the direct map. Still, we cannot prove negative and it could happen that there is a workload that would suffer a lot from the direct map fragmentation, so having a pool of large pages upfront is better than trying to fix it afterwards. As we get more confidence that the direct map fragmentation is not an issue as it is common to believe we may remove the pool altogether. I think that using PMD_ORDER allocations for the pool with a fallback to order 0 will do the job, but unfortunately I doubt we'll reach a consensus about this because dogmatic beliefs are hard to shake... A more restrictive possibility is to still use plain PMD_ORDER allocations to fill the pool, without relying on CMA. In this case there will be no global secretmem specific pool to exhaust, but then it's possible to drain high order free blocks in a system, so CMA has an advantage of limiting secretmem pools to certain amount of memory with somewhat higher probability for high order allocation to succeed. > or you need a careful access control Do you mind elaborating what do you mean by "careful access control"? > or you need SIGBUS on the mmap failure (to allow at least some fallback > mode to caller). As I've already said, I agree that SIGBUS is way better than OOM at #PF time. And we can add some means to fail at mmap() time if the pools are running low. -- Sincerely yours, Mike.