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b=V1CouIPD1awmOYL+8dafrrc0ZGcALseByYGhEf8nTxVKjeFNTjjxeCp7KKlzjFjEk ir9GSrQVjfc0F+MLVK4jjOnjjiS/AFmJz3fw9v6XS/yuamlG//eJ2kynfrqw16aa0M pbTLmzObydHP2DyvMAXa+5WyUnOPzomurWi06ilBoCvn6mcyn7tBaIWjUZrVHKVMU4 ChZOzYrplYc5L9pqwHt0DF+QLcRomY8++DxqGozZdd0CcU19/1qAdCAYYoon/9iTH2 5Zjvd05mTDJFuoAJBYnh9mwVyO+fXamJ4kPTzh3MI2DGbxSslZoxzk0JX1uYl6aCPh ywnV3+02y6w/g== Message-ID: <18392c52-a635-4d7e-856d-6203c4967483@kernel.org> Date: Tue, 20 Oct 2026 09:21:19 +0200 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/page_alloc: let the highest memory node recover from hopeless state Content-Language: en-US To: "Gregory Price (Meta)" , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, surenb@google.com, mhocko@suse.com, brendan.jackman@linux.dev, hannes@cmpxchg.org, ziy@nvidia.com, flyinrm@gmail.com, stable@vger.kernel.org References: <20261019184850.3427905-1-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-Server: rspam12 X-Rspamd-Queue-Id: B153F1A0007 X-Stat-Signature: yy3zcw63ykyroctn9sewqp955fhb3oky X-Spam-Status: No, score=-17.6 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-Rspam-User: X-HE-Tag: 1792480884-480317 X-HE-Meta: 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 3zJ0W75r 4EOkeoNYf5PJ+w0NuBS80w93p7SLbvISOU6HvxiaNE7zMLKinu8UvMrh9FS/SbyKgdfHicCSZ7AvOlVAajNJxcPlb2tM48aJpfMjmlHiHgMH4s96T+QmNJiMNkkHHTwf2VzYZ1cQe24LQVt0FdHHS0yNCiwPA7sB8zuvnJ+JAyY6DcYiPYCQgi0JmKpSj1XTsat8yGkQ60ssWqkgndu5RNBEEsVRoEcuSPw2Pqf6wWmILKsd3WCf+j3NXvDSglXW+Uox+qh6pqUGpk7J7ZqeXPh/rFr3pGS3/VNxw1+/gOl600BNdAN1HRLLHox0Db49gipu+5NMBe9plwaqfT1Cfa9OiGw8K/ifBZa1ohAATQsorapP2PyjattjW35+tb/Nf42N7dkFNbo2085w= 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 10/19/26 20:48, Gregory Price (Meta) wrote: > free_frozen_page_commit() clears a hopeless node's kswapd failures once > its zone recovers above the high watermark, but only if another memory > node exists for allocations to fall back to. > > The test `next_memory_node(nid) < MAX_NUMNODES` finds only memory nodes > with a higher id. The highest-numbered memory node therefore never > recovers on this path, and its kswapd stays disabled until reclaim on > that node makes progress and balances it, or demotion is re-enabled. > > In many cases, direct reclaim many never fully run against a lower > node (CXL/kmem), and that means its kswapd can end up full disabled > in rare situations. > > To reproduce, fill the highest memory node with bound, non-THP anonymous > memory and no swap until kswapd gives up, then free it: /proc/zoneinfo > keeps showing node_unreclaimable 1 for that node. A lower node recovers. > > Count the memory nodes instead. Adding first_memory_node != nid to the > existing test would also work, but a count says directly what the check > means: some other memory node exists. > > Fixes: e7a5f249e6db ("mm: re-enable kswapd when memory pressure subsides or demotion is toggled") > Cc: stable@vger.kernel.org > Signed-off-by: Gregory Price (Meta) LGTM enough for a stable hotfix Acked-by: Vlastimil Babka (SUSE) > --- > mm/page_alloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 417c427b196d9..6d4f03faf96ee 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2929,7 +2929,7 @@ static bool free_frozen_page_commit(struct zone *zone, > * kswapd work again by resetting kswapd_failures. > */ > if (kswapd_test_hopeless(pgdat) && > - next_memory_node(pgdat->node_id) < MAX_NUMNODES) > + num_node_state(N_MEMORY) > 1) > kswapd_clear_hopeless(pgdat, KSWAPD_CLEAR_HOPELESS_PCP); > } > return ret;