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 92B2241D127 for ; Wed, 12 Aug 2026 10:11:49 +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=1786529510; cv=none; b=HkYgHMaDMv0tSjdutQAGRwaGSJMr5cT7tRtTT2OnoUsDFuTuyJAq4hWWXs3hBbbYIJ/WXfe71wVLNPJK7hHQE0v4953WW7uwzzeGAteMOI3iwghr/sj5fKy9FZJpbLqXowOHIOEZ9HLPmvq7jRtaUd/sRFyJR1hOcB3d0EvhEBI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786529510; c=relaxed/simple; bh=z/97rXXs/YIEh9jDGriGWk0wPUaSz2b9RTQdGFikWxM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=kkAUZWIAfbysnwBAfRcU/iWYsr40DluvDq/n9fpN9LUQg8fdSvmlOKRdztmY9mEVeaZFfQOhL5bYipFxTWk1fVpNORv5j9NTkN//xzd7rDFKJzqU0aUBcrsI5idgLdnXBP46JyGU2s2lXsfRAS7zRmtNdRGfte0SOehEfJcdJu0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BpDBRWmJ; 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="BpDBRWmJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BDE691F000E9; Wed, 12 Aug 2026 10:11:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786529509; bh=ZfiNVLASDPWGps0IGQrXX1id980cU77uk3nFkKyJv+4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=BpDBRWmJG3c0g/DZXp16rkvkaW9dawtxRgwq2k2Sq3WDJ4bNN5qyuajlKSdjkVRIh /2fbVI8CIlrykXcg7GLM2kcZJq6KWr5s6Wmgn6aJwzWlZWIavul2iAdflgUY5AFQTf pdz7UKQyTd0+Dx0cwSW8F1SVzsd/dRncVdGOJmPy5nml3ku1Wn3X6pQLFZ6Juta+WI Trcl//YPJxAT/nFNY5VF5zZDEL1LkGbgifBCcS5Cw79TeCwNUj1rKOasM+zfwQi9Xv hEr69JMZ31siM9nYeji2HD/VrpP9VHvC6YT5IzZCSTmRwET1WF6+1vj1xg5WE5Q5vd gh/PUFfBKgDlg== Message-ID: Date: Wed, 12 Aug 2026 12:11:44 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 1/2] mm/memory_hotplug: optimize zone contiguous check when changing pfn range To: "Liu, Yuan1" , Oscar Salvador , Mike Rapoport , Wei Yang Cc: "linux-mm@kvack.org" , "Zou, Nanhai" , "Deng, Pan" , "Li, Tianyou" , Chen Zhang , "Zeng, Jason" , "linux-kernel@vger.kernel.org" References: <20260723084946.189392-1-yuan1.liu@intel.com> <20260723084946.189392-2-yuan1.liu@intel.com> <2cbd42e1-b5bb-474c-b0e7-ce3f46541891@kernel.org> <0b02ef3e-363f-4b49-a208-54cdfea56c75@kernel.org> <01795519-54e8-4ed8-a94e-2b77780abc3a@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/12/26 11:17, Liu, Yuan1 wrote: >> -----Original Message----- >> From: David Hildenbrand (Arm) >> Sent: Tuesday, August 11, 2026 8:23 PM >> To: Liu, Yuan1 ; Oscar Salvador ; >> Mike Rapoport ; Wei Yang >> Cc: linux-mm@kvack.org; Zou, Nanhai ; Deng, Pan >> ; Li, Tianyou ; Chen Zhang >> ; Zeng, Jason ; linux- >> kernel@vger.kernel.org >> Subject: Re: [PATCH v6 1/2] mm/memory_hotplug: optimize zone contiguous >> check when changing pfn range >> >> On 8/10/26 16:04, David Hildenbrand (Arm) wrote: >>> >>> Thanks for reminding me. I think the right direction is to finally clean >> up the >>> pfn_valid() handling. >>> >> invalid >> subsection >> follows >> going >> wrong. >> which >> through >> the hole, >> zero-filled >>> Let me take a stab at just having pfn_valid() / for_each_valid_pfn() >> respecting >>> the subsection map. >> >> ... and that turns complicated very quickly. The problem is that we have >> some users, >> in particular the buddy, that just assumes that MAX_PAGE_ORDER regions are >> fully >> accessible. >> >> The fun begins once we have MAX_PAGE_ORDER span multiple subsections. So >> we'd actually >> want to initialize the memmap. >> >> The pfn_valid() vs. pfn_to_online_page() inconsistency is really nasty :( >> >> I mean, in init_unavailable_range() we could actually figure out fairly >> easily >> whether we are dealing with holes where pfn_to_online_page() would >> succeed. >> >> diff --git a/mm/mm_init.c b/mm/mm_init.c >> index e9c4204b73adb..54e71e17f2c3c 100644 >> --- a/mm/mm_init.c >> +++ b/mm/mm_init.c >> @@ -843,11 +843,13 @@ static void __init init_unavailable_range(unsigned >> long spfn, >> int zone, int node) >> { >> unsigned long pfn; >> - u64 pgcnt = 0; >> + u64 pgcnt = 0, online_pgcnt = 0; >> >> for_each_valid_pfn(pfn, spfn, epfn) { >> __init_single_page(pfn_to_page(pfn), pfn, zone, node); >> __SetPageReserved(pfn_to_page(pfn)); >> + if (pfn_to_online_page(pfn)) >> + online_pgcnt++; >> pgcnt++; >> } >> >> If it's a problem performance-wise, we can always try optimizing by >> skipping >> checks within the same (sub)section. > > Hi David > > What about the following approach to skipping the check within the same > (sub)section? > > @@ -827,11 +827,21 @@ static void __init init_unavailable_range(unsigned long spfn, > int zone, int node) > { > unsigned long pfn; > - u64 pgcnt = 0; > + u64 pgcnt = 0, online_pgcnt = 0; > + unsigned long last_subsection = -1; > + bool is_online = false; > > for_each_valid_pfn(pfn, spfn, epfn) { > + unsigned long subsection = pfn & PAGE_SUBSECTION_MASK; > + > __init_single_page(pfn_to_page(pfn), pfn, zone, node); > __SetPageReserved(pfn_to_page(pfn)); > + if (subsection != last_subsection) { > + is_online = !!pfn_to_online_page(pfn); > + last_subsection = subsection; > + } > + if (is_online) > + online_pgcnt++; > pgcnt++; > > If this looks good, let me prepare and send out the next version series. Yeah, something like that should do. -- Cheers, David