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b=VtievZEidSVJKJ8wgbiTyLqG2cFPhE5Pkzw8ITYYjhGHuopw91uKJ9JtJJdRSMp7F M2UqZkhfBFg1lLeA8FWkN2BhW/bw5tRWjEgKb5mCzZHqQhOKiRyb5dBXGRNKduN/C/ HdJX54ceYFkIb/lIpcSEH7JL9BNLd2+wXtYeqxBfrzz35lBQkZFDs2sMw+rNalIzlZ H/Yz0Rg0YFmSD1A+4EfXPNMfRbhHRh9eLrQyrr6++JrV5sREhUgg9l3wqbVMCRXPBU 116/V5xj5GH0fxIc/woLjEPZOKHPaBaWmzSg1SSYfwsx5cyHxvemiTdvhRWAnXNXkI z1GGNTHz/rJGg== Message-ID: <7a1807d0-4f3b-4094-b73b-b6950040e3ab@kernel.org> Date: Thu, 29 Oct 2026 19:10:19 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 7/8] mm/page_alloc: retry alloc_contig_pages() when the zonelist is rebuilt Content-Language: en-US To: "Gregory Price (Meta)" , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, muchun.song@linux.dev, osalvador@suse.de, david@kernel.org, akpm@linux-foundation.org, ziy@nvidia.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, ying.huang@linux.alibaba.com, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, brendan.jackman@linux.dev, hannes@cmpxchg.org, mgorman@techsingularity.net, anshuman.khandual@arm.com, stable@vger.kernel.org References: <20261028211930.3504634-1-gourry@gourry.net> <20261028211930.3504634-8-gourry@gourry.net> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 66801160006 X-Rspam-User: X-Stat-Signature: 15ugcphj3678h9niof9yat91c5zoo9uy X-Spam-Status: No, score=-17.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam03 X-HE-Tag: 1793297426-270394 X-HE-Meta: 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 mXVFwpS0 ZMOrcB+JICPaBmY2F9EkiKQfAcjOoo7gTdPIMFSNgR2WN6BgXJ3V60qjaYArTnz88yZ4D0t+RDi+vlK4KxAB0ZfSqyGxrwzdiCax22wnM7undPPrQbAWmVolW5HXeYRn45Vbmb/X+q3MQ/JAD/wkTABzdct6sj9u0BBvCbRqK9R6OlkS2XovIWlK/NicfDR2dycWTvi8zMsisK6RfKsUS2XJ2BgNUc3wqv6W39/YwES6uInISE5Jv2hbsjzgslFFgLx+VPchLoldcwvn81dFa1G+MkvKYe8SFacnlwr1dvB4Ht+BiQo5ncNjz0g8f4bpBJbogTetNyMgx7QikXtMcPU7D3EvN9hmbQ/hXshRtm13HwmVRSCYa55b6D5xFl9yOJpfszrWhlCg70SctuomnvEp9CyY8YLC0VKQQaYBr3mr5mLymbQ3S0S2d8R57V7llvrfOVE6ICppWdkRL5WWt2+rfNQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 10/28/26 22:19, Gregory Price (Meta) wrote: > Onlining the first block of a zone rebuilds every zonelist in place, > shifting the slots after the new zone. > alloc_contig_frozen_pages_noprof() approves a slot by the caller's gfp > and nodemask, then loads the zone from it: > > CPU 0 CPU 1 > alloc_contig_frozen_pages_noprof(GFP_HIGHUSER | __GFP_THISNODE) > slot 0 (NORMAL1) approved > online_pages() > build_all_zonelists() > [NORMAL1] > -> [MOVABLE1, NORMAL1] > zone = zonelist_zone(slot 0) /* MOVABLE1 */ > alloc_contig_frozen_range(MOVABLE1 pfns) > > A gigantic hugetlb page can then land in ZONE_MOVABLE, and a nodemask > caller can get a range from another node. Gigantic pages are kept out > of ZONE_MOVABLE since commit 79b63f12abcb ("mm, hugetlb: do not allocate > non-migrateable gigantic pages from movable zones"). > > Check zonelist_update_seq before using each zone, and restart the walk > if it changed, as the hugetlb pool walk does. Check again before > escalating to the pass that may migrate hugetlb pages, so a pass a > rebuild cut short is redone rather than escalated. > > With kprobes holding the walk across the online, the base kernel put the > 1G page in ZONE_MOVABLE in 3 of 3 runs, and this change put it in > ZONE_NORMAL in 3 of 3. Direct GFP_KERNEL calls with nodemask {1} and > {2} got a ZONE_MOVABLE range and a node 1 range on base, 3 of 3 each, > and neither with this change. > > Fixes: 5e27a2df03b8 ("mm/page_alloc: add alloc_contig_pages()") > Cc: stable@vger.kernel.org > Signed-off-by: Gregory Price (Meta) Reviewed-by: Vlastimil Babka (SUSE) > --- > mm/page_alloc.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 70830689048a..7d06c6c4011a 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7593,6 +7593,7 @@ struct page *alloc_contig_frozen_pages_noprof(unsigned long nr_pages, > gfp_t gfp_mask, int nid, nodemask_t *nodemask) > { > unsigned long ret, pfn, flags; > + unsigned int zonelist_cookie; > struct zonelist *zonelist; > struct zone *zone; > struct zoneref *z; > @@ -7601,8 +7602,13 @@ struct page *alloc_contig_frozen_pages_noprof(unsigned long nr_pages, > > retry: > zonelist = node_zonelist(nid, gfp_mask); > + zonelist_cookie = zonelist_iter_begin(); > for_each_zone_zonelist_nodemask(zone, z, zonelist, > gfp_zone(gfp_mask), nodemask) { > + /* A rebuild may have shifted an ineligible zone into this slot. */ > + if (unlikely(check_retry_zonelist(zonelist_cookie))) > + goto retry; > + > spin_lock_irqsave(&zone->lock, flags); > > pfn = ALIGN(zone->zone_start_pfn, nr_pages); > @@ -7637,6 +7643,9 @@ struct page *alloc_contig_frozen_pages_noprof(unsigned long nr_pages, > * second pass, we will try moving HugeTLB pages when those pages are > * smaller than the requested contiguous region size. > */ > + /* Redo a pass that a rebuild cut short before escalating. */ > + if (unlikely(check_retry_zonelist(zonelist_cookie))) > + goto retry; > if (skip_hugetlb && skipped_hugetlb) { > skip_hugetlb = false; > goto retry;