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 84B38CD6E52 for ; Sun, 31 May 2026 18:51:23 +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:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: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=FAxCb8wt4MDofHdr7bDysjYqqW+0dO2zfePgF4EMiLc=; b=2mv4TIDzcF/wGCifLJUzjYw3hc rDxrRfUBAGLomS7mp1iVwV4v35Vo20mDRqH/AOY1TjVaj4iV1jntGaAlx/7vrmrJlGCH6QrZMS+H7 CLBRmYSh2o4jaLYMMJSqcjLL3IRkXUe8vh0P8cwrPB1AoXWDFDopzxaBBfBg5480h17t48Ss1o+WE oSaEg2lKjDrpJyOQfpn1JoEoEXiH8uTTg29B5Clbdv4NyVNDj9muudmyCtvNqm1TNO0Zy9Jju5Ei3 HzkaN+jx9dRFqrWRA84sv1s4EdI8ZMAm/dDpwyEW0KyiVzOnVKPq+jtweO8hGzuCzMZp6f63WJaSh 6RtdI3tA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wTlFp-00000009pal-2XxO; Sun, 31 May 2026 18:51:21 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wTlFn-00000009pae-3hWG for kexec@lists.infradead.org; Sun, 31 May 2026 18:51:19 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 736826008A; Sun, 31 May 2026 18:51:17 +0000 (UTC) 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2vxzse7j7ai9.fsf@kernel.org> 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 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.