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h=Date:From:To:Cc:Subject:References:In-Reply-To; b=mMAaxlNnxdyl4mQxQyS/wkmDUx3chMaHciqE9DrDRwHke7Oyow2NxXwO8bFqHRs6Z HQ/HbnfmXSgMapZcx//yZOtdcpBvP1pr2FSVxJyLQ/2CiIc9xqC+wc0IF48YOihe95 KVzUKgKfirySdLJY0oXOyyaUWo12vbxHe8UNYJMa0eCkfqlZM3bZFFcPPRXaNM5X6u gzQCnmP5s+lGJjhCJ6m7ObDGNU0MUiVSgRTN/XfCTi6Fr75Dx+NlUlicWK2IqCFWjA OfqeeLZaMsCBzYq3GhCQkALmwm5CtO4MiEpo0SqgdfLs6RCF0yheIC/HXVxKr8dJq4 Xn+Cg1UCgEWxg== Date: Tue, 15 Sep 2026 09:03:52 +0300 From: Mike Rapoport To: Yuan Liu Cc: David Hildenbrand , Oscar Salvador , Wei Yang , linux-mm@kvack.org, Nanhai Zou , Chen Zhang , Jason Zeng , Chen Yu , Pan Deng , Tianyou Li , linux-kernel@vger.kernel.org Subject: Re: [PATCH v9 2/2] mm/memory_hotplug: optimize zone contiguous check when changing pfn range Message-ID: References: <20260914072929.1883794-1-yuan1.liu@intel.com> <20260914072929.1883794-3-yuan1.liu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260914072929.1883794-3-yuan1.liu@intel.com> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: D336CC0004 X-Rspam-User: X-Stat-Signature: pyaxrkfdrp6qw6posppttio5f7sunndz X-HE-Tag: 1789452240-56153 X-HE-Meta: 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 5a+deCy2 Y4DUZVr5RTH42SKYqJ8nmtgxtP0zsgKlowCsWcXJhuH1WxbZMAWvbVFk9O+RUs6CYFmEplEU9ROqlJExP41FaMO1cMAM83KanPnjtLZBemQgelLuVaKLtRsBIbG0cSgbJWA61I2LtCLySUorCI5CPbZYRGEhrcV7IV0+mUevl2pGWmI3klWiYzG8nAc4GBpdQwxoRyCjBd6onSAzLQcHreUeVfG2gvbUh7Mt6yxp/BSgrJf+fMX70EzbbhmKAjGA6EI187UTlB+eiGQECJ9N9iuyr3nKoNWSppxSvsayIHDgwgW8tosO605QdLUGKkvUJos5itXSkQdYd119wXnMXOaeNPaGR5Ila3ZdlzvRNi8Lhr2w6ugMUqc/OXTwRoJxaS8xGBM1CZX+2gaiqJkp7XWNrww== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi, On Mon, Sep 14, 2026 at 03:29:29AM -0400, Yuan Liu wrote: > When move_pfn_range_to_zone() or remove_pfn_range_from_zone() updates a > zone, set_zone_contiguous() rescans the entire zone pageblock-by-pageblock > to rebuild zone->contiguous. For large zones this is a significant cost > during memory hotplug and hot-unplug. > > diff --git a/mm/mm_init.c b/mm/mm_init.c > index 1533aebafb68..d40a8ff23370 100644 > --- a/mm/mm_init.c > +++ b/mm/mm_init.c > @@ -817,22 +817,39 @@ void __meminit init_deferred_page(unsigned long pfn, int nid) > * zone/node above the hole except for the trailing pages in the last > * section that will be appended to the zone/node below. > */ > -static void __init init_unavailable_range(unsigned long spfn, > - unsigned long epfn, > - int zone, int node) > +static unsigned long __init init_unavailable_range(unsigned long spfn, > + unsigned long epfn, > + int zone, int node) > { > + unsigned long next_chunk_pfn __maybe_unused = spfn; > unsigned long pfn; > - u64 pgcnt = 0; > + u64 online_pgcnt = 0, pgcnt = 0; > + bool is_online = true; > > for_each_valid_pfn(pfn, spfn, epfn) { > __init_single_page(pfn_to_page(pfn), pfn, zone, node); > __SetPageReserved(pfn_to_page(pfn)); > pgcnt++; > + > + /* > + * With vmemmap, at this stage all pages in an early section > + * have a valid memmap and are marked as online. However, only > + * subsections in the subsection map are actually online. > + */ I'm having trouble parsing this comment. Shouldn't is say that some subsections in a section can be offline because of holes? Other than that Acked-by: Mike Rapoport (Microsoft) > +#ifdef CONFIG_SPARSEMEM_VMEMMAP > + if (pfn >= next_chunk_pfn) { > + is_online = pfn_section_valid(__pfn_to_section(pfn), pfn); > + next_chunk_pfn = min(SUBSECTION_ALIGN_UP(pfn + 1), epfn); > + } > +#endif > + if (is_online) > + online_pgcnt++; > } > > if (pgcnt) > pr_info("On node %d, zone %s: %lld pages in unavailable ranges\n", > node, zone_names[zone], pgcnt); > + return online_pgcnt; > } > > /* -- Sincerely yours, Mike.