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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 11406CD5BB0 for ; Fri, 22 May 2026 15:02:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:MIME-Version: Message-ID:Date:References:In-Reply-To:Subject:Cc:To:From:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=A2IrT8PydzK9xxtu2jbeHfoX/1GcdXru7uVPffwnQVk=; b=dL0sLKFcylD125SydbUQVEbfTn z4K1m/sJab6TuuCBGH8M+luSjjDwCKSD4s1VJPxj/T1ZXoEeoMsqTTQK/rdfLLWzTQy/OfIxrfdKO 7PW03y7NdlLCkjGBtUistSXpuvQXqU48kPp9OWyH1Jh1IZZCAnbBqRTpZHMcpuyxTLWEN2MnFlnnh jJrMSRJg0MYcHX1rxy6e9X/2Dn2IQYN25AL6M6O44KX6s+/OGZqwCVq5cqoCcgOQ8dF6+QHHl0paU wxP+2gdcyH5/w4WyI3dIxhbkPme0hC2d3CdUTA62F5OBR6M01dMCQtvVJAchfiUfQikRzeXo2KPXQ Hl4lDNrA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wQROf-0000000BCWl-1u28; Fri, 22 May 2026 15:02:45 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wQROd-0000000BCW2-0EUT for kexec@lists.infradead.org; Fri, 22 May 2026 15:02:44 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 57D08404C1; Fri, 22 May 2026 15:02:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5E1C61F000E9; Fri, 22 May 2026 15:02:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779462162; bh=A2IrT8PydzK9xxtu2jbeHfoX/1GcdXru7uVPffwnQVk=; h=From:To:Cc:Subject:In-Reply-To:References:Date; b=KrfS+tJBjhwvjCQc5lgSC6UFM6xUBTGfKJwHZGomUl3hmvnG1kj0ilOsmwLMOtvHs WkhRDeIH8FQct/ouklVCLMRrJcS4BKjeoi4U6HGiK3BZ7DhLP+gUuvdgdIKhpD1yeQ pKpFA76LjjW6sjKy3COwgf521ZIPorDv2JVVq+AP9nJYDkyGweg+5VRbvMyV65K+OV aMVCLwYyHtObaRLTb86V3MFbGhyycqmQnZ3xtdjEd0oeePDe/GK6oTq4Io2R0xvTOH DZcT6S+Tdy/0Ntak24i/r+mUMrhP0rIdIsr01sIslAsOIJMLNw/ikjSgkesOrd/DOv rfHbxnVUM2xoA== From: Pratyush Yadav To: Pasha Tatashin Cc: Pratyush Yadav , Mike Rapoport , Alexander Graf , Muchun Song , Oscar Salvador , David Hildenbrand , Andrew Morton , Jason Miu , kexec@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 09/12] memblock: introduce MEMBLOCK_KHO_SCRATCH_EXT In-Reply-To: (Pasha Tatashin's message of "Fri, 22 May 2026 00:48:35 +0000") References: <20260429133928.850721-1-pratyush@kernel.org> <20260429133928.850721-10-pratyush@kernel.org> <2vxzecjhc2s8.fsf@kernel.org> Date: Fri, 22 May 2026 17:02:38 +0200 Message-ID: <2vxzse7j7ai9.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260522_080243_137761_610B84D1 X-CRM114-Status: GOOD ( 30.91 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On Fri, May 22 2026, Pasha Tatashin wrote: > On 05-11 18:46, Pratyush Yadav wrote: >> On Mon, May 11 2026, Mike Rapoport wrote: >> >> > On Wed, Apr 29, 2026 at 03:39:11PM +0200, Pratyush Yadav wrote: >> >> From: "Pratyush Yadav (Google)" >> >> >> >> In the upcoming commits, the KHO will learn how to discover free blocks >> >> of memory by walking the KHO radix tree. It will then mark those regions >> >> as scratch to allow memory allocation in case scratch runs low. >> >> >> >> To differentiate the extended scratch areas from the main scratch areas, >> >> introduce MEMBLOCK_KHO_SCRATCH_EXT. Use it when choosing memblock flags >> >> for allocations during scratch-only. Teach should_skip_region() to check >> >> for both flags before deciding if the region should be skipped. >> > >> > Why there's a need to differentiate SCRATCH and SCRATCH_EXT? >> > SCRATCH (I still hate the name) means "memory memblock can safely use for > > +1000 > > I also strongly dislike this name and mentioned it in another thread > earlier today. > > If we ever decide to s/scratch/something-else/ globally, that should be a > separate cleanup effort. However, since we are introducing a brand new flag > here, we can discuss a better name for the _ext portion to avoid overloading > the "scratch" concept. > >> > the allocations". Initially this memory comes from the reservations in the >> > first kernel, but if the second kernel can find more memory to extend it, >> > why that additional memory should be treated differently? >> >> Two reasons: >> >> 1. We mark SCRATCH as MIGRATE_CMA. We don't want to do that for >> SCRATCH_EXT since this memory can be used for non-movable >> allocations. >> >> 2. Gigantic (1G) huge pages can not be allocated from scratch. They can >> be preserved memory and thus should not be allocated from SCRATCH. >> See patch 12 that does allocations for gigantic huge pages only from >> SCRATCH_EXT. >> >> I will add this in the commit message for the next version. >> >> Naming is hard, so if you have any better names I'm all ears :-) > > IMO, this scratch_ext is not "scratch" in the traditional KHO sense at all. > The traditional KHO scratch is what is passed from kernel to kernel and is > guaranteed to contain zero preserved memory. This new memory is not passed > from kernel to kernel and can contain preserved memory at runtime. It's > essentially just memory that we identify as currently unpreserved and release > early to the system. > > If we want to keep the naming aligned with the existing codebase for now: > MEMBLOCK_KHO_SCRATCH -> original scratch > MEMBLOCK_KHO_UNPRESERVED -> for the new memory (instead of SCRATCH_EXT) UNPRESERVED sounds good to me. I will use that for the next revision unless Mike objects. > > Alternatively, if we do want to tackle the global rename of "scratch" later: > MEMBLOCK_KHO_BOOTSTRAP -> for the original scratch > MEMBLOCK_KHO_UNPRESERVED -> for this new dynamic memory Or perhaps BOOTMEM? I suppose either of the two are somewhat better than scratch. Anyway, can we please do the SCRATCH rename as a separate series? I would like this series to not get muddled in the naming discussion. I will use UNPRESERVED for the new concept in v2 though. > > What do you think? > > Pasha -- Regards, Pratyush Yadav