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 00D9D3A7848 for ; Sat, 26 Sep 2026 09:07:03 +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=1790413625; cv=none; b=ChwzqPfXM+FGKXNdULY8IF837cpVAi0yEH1K92qWcH7+7GNTUwBK6sfmKKxQ+xi377lLsCqBw10t7O+/69hrcDb7TOAT+tiXXPp6rMMs3PC67AMO6Apx5U0ly8XhQ3K9fnRfiMi4cTnDju6bBdEDh8eKzyQmBZYRv+6Tk+LKX3s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790413625; c=relaxed/simple; bh=WvfBGpR1GBcOSA8H2wzRgak34aXBgjkHoqzet2bCmX0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PIgTZFlgylzjw3I80OSobJapeU9cbW0oxk3Rc7yOUW7I/tLe9XZC+SH9DwM/5h8tvbeZEzpkloQzgE99zzAWZWWceCs7JPmfEMWYQmGGnWsIF+bScsfcrhF+tnLStnTczIRI4H3WTzUSQajOTxfw9I+CAy6MuVV5P2b5CuIp20I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lf0MJXkU; 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="lf0MJXkU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 491B71F000FF; Sat, 26 Sep 2026 09:06:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790413623; bh=0MN7/YNmFykM+Q/E4Xx2sgObdvP7k1Pyx2eBjEnQm+E=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=lf0MJXkUoYjmOO8Zwb8vIvA5uxqyFRr42qmD8bpiiuuc+YlAQbA5FZg6WmohA2S2W BcPl9Ua2Y0vA4e5sWNQ3N6sorsf4zmkGr6JurTKOEYK2RyUDThaUTviF8/8BfUJI/p 8Y4Z+1XRSq0Vk1au3yRFRfptTt1kf1NiZ5T5g//k6ePXa/exIUNtQWRqREzz8jscJU fH+5pnTW869euEUnAZfj/UmTB5EJDr9D7CJC0N1XSRyWETcOOFTKXG7X0rmY6kKoRv hVimUOo8K8gOAtJioFv225DwUSJ/4Je4ZgWAWEl5vBmdYO0/4AftlodYCTfj+23udv ecAcwpbb0lQ8Q== Date: Sat, 26 Sep 2026 12:06:56 +0300 From: Mike Rapoport To: Sourabh Jain Cc: kexec@lists.infradead.org, Alexander Graf , Andrew Morton , George Guo , Pasha Tatashin , Pratyush Yadav , "Ritesh Harjani (IBM)" , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] kho: fix global scratch size calculation Message-ID: References: <20260922131217.698809-1-sourabhjain@linux.ibm.com> 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: <20260922131217.698809-1-sourabhjain@linux.ibm.com> Hi Sourabh, 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. > > On powerpc, the difference can be seen in the scratch_len values > reported by: > > cat /sys/kernel/debug/kho/out/scratch_len > > Before this change, the global scratch allocation was 0x12000000 > (288 MB): > > 0x1000000 (16 MB) > 0x12000000 (288 MB) <- global allocation > 0x5000000 (80 MB) > > After this change, the global scratch allocation is 0xd000000 > (208 MB): > > 0x1000000 (16 MB) > 0xd000000 (208 MB) <- global allocation > 0x5000000 (80 MB) > > The 80 MB difference is the per-node reservation that was previously > being included in the global allocation. > > The same issue also affects lowmem scratch memory, but its impact is > limited because the lowmem scratch memory calculation is restricted to > the first 4G of memory. The changes also cover the lowmem scratch > memory case. > > Cc: Alexander Graf > Cc: Andrew Morton > Cc: George Guo > Cc: Mike Rapoport > Cc: Pasha Tatashin > Cc: Pratyush Yadav > Cc: Ritesh Harjani (IBM) > Cc: linux-kernel@vger.kernel.org > Cc: linux-mm@kvack.org > Signed-off-by: Sourabh Jain > --- > include/linux/memblock.h | 1 - > kernel/liveupdate/kexec_handover.c | 49 ++++++++++++++++++++++-------- > mm/memblock.c | 22 -------------- > 3 files changed, 37 insertions(+), 35 deletions(-) > > diff --git a/include/linux/memblock.h b/include/linux/memblock.h > index d62db9e776cf..678fe466529a 100644 > --- a/include/linux/memblock.h > +++ b/include/linux/memblock.h > @@ -487,7 +487,6 @@ static inline __init_memblock bool memblock_bottom_up(void) > phys_addr_t memblock_phys_mem_size(void); > phys_addr_t memblock_reserved_size(void); > phys_addr_t memblock_reserved_kern_size(phys_addr_t limit, int nid); > -phys_addr_t memblock_reserved_hugetlb_size(phys_addr_t limit, int nid); > unsigned long memblock_estimated_nr_free_pages(void); > phys_addr_t memblock_start_of_DRAM(void); > phys_addr_t memblock_end_of_DRAM(void); > diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c > index 7c4d86daf86d..dc809e1e768c 100644 > --- a/kernel/liveupdate/kexec_handover.c > +++ b/kernel/liveupdate/kexec_handover.c > @@ -752,6 +752,31 @@ static int __init kho_parse_scratch_size(char *p) > } > early_param("kho_scratch", kho_parse_scratch_size); > > +static phys_addr_t __init_memblock memblock_reserved_size_nid(phys_addr_t limit, int nid, > + enum memblock_flags region_type) > +{ Why is this in kexec_handover.c and not in memblock.c? > + struct memblock_region *r; > + phys_addr_t total = 0; > + > + for_each_reserved_mem_region(r) { > + phys_addr_t size = r->size; > + > + if (r->base > limit) > + break; > + > + if (r->base + r->size > limit) > + size = limit - r->base; > + > +#ifdef CONFIG_NUMA > + if (nid == memblock_get_region_node(r)) > +#endif Do we really need the #ifdef here? > + if (r->flags & region_type) > + total += size; > + } > + > + return total; > +} > + > static void __init scratch_size_update(void) > { > /* -- Sincerely yours, Mike.