From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 99D2F22D4C3 for ; Sun, 31 May 2026 18:51:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780253478; cv=none; b=oaBx0Csh6Y27t+SK1C1ycklPUUXIjCvOG15eRWNvk/YLCNBvl3lr/AOsg+0GKFcAAw4f2rXbrN8o48g0Y1zSs5T5PZ9vJQBqaBMhh/yE/MclgqhRifj59+xWR8n/1K8JnzI7RWky63JXNlan8Rilx89BHlHjqWKb8PvI46A0Aj8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780253478; c=relaxed/simple; bh=/Cgi3aMb+YBZc7HOAkMMOqL2wa3tc6wUSeuKA0eiAxI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mhxOZRTC8PmxBpsl4W0m59RJDACOYOxFiVO8nzKA47d4kBCPLBNiAfegyDr4p4jAa2h8PK9S50pznvwKgmYAdRHCLvc25+OksuKSy5IGDikqk6FtNyqg7FUbzRWIVysirVWaS3zvSJlqK07bemczaXSdCXLrNl1Qa2WfLlyDfVo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=G+RQr4Xc; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="G+RQr4Xc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 51E041F00893; Sun, 31 May 2026 18:51:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780253477; bh=FAxCb8wt4MDofHdr7bDysjYqqW+0dO2zfePgF4EMiLc=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=G+RQr4XcxsfKqn/e3SCfS3h9uirQNGVtyU7yFFUFtiaMRwqJpqhfubECNmUCiGK8P YRX5pdjgi775fLQnPYtqhj26Lye5uqnK6D5co+pxhbEIfh1NlRlA1QGfLxlYTVUxKO KhvpfEzmKfkvYVUhJgR21RNGCsHz24aAwBlNjDY6wQ6rBBuNOeDL3Q8dU2e56E8M4q pDJrM3jMgyDlbzB+Q3tELtdfGg7ZrnSoE3Ht4caejeMbAt2e5hbvbpdjt0fnbGKM4w 6JYGnMwpbOlQdzWvpfqSL194r6Tq0eE+YauGMYOh5UD9qOapZm6PoN83BK6DXX02kw V5xsWw1ScHvnQ== Date: Sun, 31 May 2026 21:51:09 +0300 From: Mike Rapoport To: Pratyush Yadav Cc: Pasha Tatashin , 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 Message-ID: References: <20260429133928.850721-1-pratyush@kernel.org> <20260429133928.850721-10-pratyush@kernel.org> <2vxzecjhc2s8.fsf@kernel.org> <2vxzse7j7ai9.fsf@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2vxzse7j7ai9.fsf@kernel.org> On Fri, May 22, 2026 at 05:02:38PM +0200, Pratyush Yadav wrote: > 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. Can we make it shorter? ;-) UNPRESERVED makes sense, although I'd love to completely remove KHO_ notion and make the name reflect how it's used by memblock. I was toying with PREFERRED instead of SCRATCH, but it didn't feel right enough. With two of them that surely won't work :) > > 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. Well, if we have BOOTMEM_HVO, we can have BOOTMEM_KHO as well :) > Anyway, can we please do the SCRATCH rename as a separate series? I Sure. We can continue bikeshedding in parallel. > would like this series to not get muddled in the naming discussion. I > will use UNPRESERVED for the new concept in v2 though. That might warrant v3 even if everything else is perfect :) > -- > Regards, > Pratyush Yadav -- Sincerely yours, Mike.