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 E8957CC6B0F for ; Tue, 13 Oct 2026 09:02:29 +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=isgOp/oWK7UgvcDokY0BIJcX1YHTkMKo0hu92B4JBqE=; b=s3Q2TRIwRF47+VNJoTTj9iq/Vs WUk308d6nb1JNo8krYnFzIL59VuNrkfa3ObHUMwPdEqQ+2+LV6a8Ta3wp1gO5FhrogZ2tixBE6OO7 b2s6fkV6Okon1GQwGjgShh6RgYTycmv2poPIS1pRhTC+kRzpdLM52I3fFKgWzdoTrNKnTVUgwAACJ myE5UKXXDMVRa3K3o9K83XFppxX6KqiOuRwVvHqTQ9ODP7+6YtdEjmueW1evHDSsyIdP1gwHjuSO2 kvV9BGdJtdCTRjoSy+NqltS/L5rBOMHXmFc+Nk4wHNYwR6IlWNDL+q0+B1KU8XCkbN3Ta4DUXec// DbrAe7kA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xGYOw-0000000COVL-15hr; Tue, 13 Oct 2026 09:02:26 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xGYOv-0000000COVE-2L0W for kexec@lists.infradead.org; Tue, 13 Oct 2026 09:02:25 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id A0C2B600D1; Tue, 13 Oct 2026 09:02:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 755671F000FF; Tue, 13 Oct 2026 09:02:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791882144; bh=isgOp/oWK7UgvcDokY0BIJcX1YHTkMKo0hu92B4JBqE=; h=From:To:Cc:Subject:In-Reply-To:References:Date; b=WSkbhZjmBqxa/sE2Mnj8bDjz5+8dGlp3i9aHxaj6Eh1hfQ0DAxLPoWWdiZURnF/ca Tvbld43AOhDlNw9YBllVvmszi7dHcPek92UyqKZQ5o2H52xrnkHnPUyUzTDXKYyNgH i0a4LNwP7m8WVeUKgeA0cOzJpeOhrIKm2Gkd3T0vDx+8dSeoAuMDXszD3w7bYhbjTE /ROYm1XgqH1+HjIvKUJTs5jBAfVkmhOy6TB5DUFKovrpNtbOX220LROmoSRL7p03mY oE+0lCVh7XqFtCADccnxOtMpR8kiH3fyURn5RbjKYISlVtrcEjCoo9x8X28TZqbfM1 ZlVGRj6iDynXQ== From: Pratyush Yadav To: Mike Rapoport Cc: Pratyush Yadav , Sourabh Jain , kexec@lists.infradead.org, Alexander Graf , Andrew Morton , George Guo , Pasha Tatashin , "Ritesh Harjani (IBM)" , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] kho: fix global scratch size calculation In-Reply-To: (Mike Rapoport's message of "Mon, 12 Oct 2026 20:11:10 +0300") References: <20260922131217.698809-1-sourabhjain@linux.ibm.com> <2vxzo6czjaa9.fsf@kernel.org> Date: Tue, 13 Oct 2026 11:02:20 +0200 Message-ID: <2vxz33uaj7mr.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain 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 Mon, Oct 12 2026, Mike Rapoport wrote: > On Mon, Oct 12, 2026 at 03:52:46PM +0200, Pratyush Yadav wrote: >> On Sat, Oct 03 2026, Mike Rapoport wrote: >> >> > On Tue, Sep 22, 2026 at 06:42:16PM +0530, Sourabh Jain wrote: >> >> KHO calculates the global scratch size based on memblock-reserved kernel >> >> memory. It passes NUMA_NO_NODE to memblock_reserved_kern_size() for >> >> this calculation. >> >> >> >> When memblock_reserved_kern_size() is called with NUMA_NO_NODE, it >> >> counts both: >> >> >> >> - memory reserved for a specific NUMA node >> >> - memory reserved with NUMA_NO_NODE >> >> >> >> KHO needs to distinguish between these two types of reservations. >> >> When calculating the size of global scratch memory, KHO only needs to >> >> account for reservations made with NUMA_NO_NODE. Reservations made for >> >> a specific NUMA node must not be included in the global scratch size. >> >> >> >> Add memblock_reserved_size_nid() to calculate reserved memory for a >> >> given reservation type and NUMA node. When NUMA_NO_NODE is passed, it >> >> counts only memory reserved with NUMA_NO_NODE. >> >> >> >> Use the new API for lowmem, global, and per-node KHO scratch size >> >> calculations. For lowmem and global scratch, count only memory >> >> reservations that were made with NUMA_NO_NODE. For per-node scratch, >> >> count only memory reservations that were made with the corresponding >> >> NUMA node ID. >> >> >> >> Remove memblock_reserved_hugetlb_size() since it has the same >> >> implementation as the new API and differs only in the memblock >> >> reservation flag being checked. The new API handles both kernel and >> >> HugeTLB reservations through its reservation type argument. >> >> >> >> Define the new helper as a static function in the KHO implementation, >> >> since it is only used by KHO and has no users outside >> >> kernel/liveupdate/kexec_handover.c. >> > >> > I looked again and this feels like a band-aid to me. >> > >> > I think we need to step back and rethink the order of the >> > scratch/kho-bootmem sizing and consider how NUMA and lowmem are involved >> > there. >> >> Could you elaborate? How else would you calculate the sizes? >> >> To me, the idea sounds fine (although I also share your comments on the >> code style). This is what the global scratch size should have been doing >> from the get-go. Today it over-allocates by counting both global >> allocations and _all_ per-node allocations. > >> There is a separate problem with CONFIG_NUMA=n, but for that I think we >> should just have a different allocation path where we only do lowmem and >> global scratch. > > I mean more fundamental code refactoring that takes into the account all > cases (and I could miss some) > > - NUMA vs no-NUMA > - systems that have global scratch containing lowmem scratch vs those that > don't > - and of course fix global scratch over-allocation Fair enough, that makes sense. [...] -- Regards, Pratyush Yadav