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From: Shakeel Butt To: "David Hildenbrand (Arm)" Cc: "Barry Song (Xiaomi)" , akpm@linux-foundation.org, linux-mm@kvack.org, baoquan.he@linux.dev, chrisl@kernel.org, jp.kobryn@linux.dev, kasong@tencent.com, liam@infradead.org, linux-kernel@vger.kernel.org, ljs@kernel.org, mhocko@suse.com, nphamcs@gmail.com, rppt@kernel.org, shikemeng@huaweicloud.com, surenb@google.com, usama.arif@linux.dev, vbabka@kernel.org, youngjun.park@lge.com Subject: Re: [PATCH v3 1/4] mm: avoid unnecessary lru drain for wp_can_reuse_anon_folio() Message-ID: References: <20260701235955.36126-1-baohua@kernel.org> <20260701235955.36126-2-baohua@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 1A8FF18000E X-Stat-Signature: jkxxcc5owtbnk5wxqj8oydwsh8nme53f X-HE-Tag: 1783437714-956853 X-HE-Meta: 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 2ZPJlI1L OysYq6Ksz8QoclFpgMtUEjbPVDfDuNLPCxqdQqZ9+iuHfpTv+51wanSP8yjejfEWQzIsm/Sqgkwv595oqCVGeqTmPqsa9BCfo2ps7gsHOV2aGhxUzZL0FCTwhwIUWNIljeXqLCrIWNTdk2wbGxe00OyPyoJYkA9EM7XIrwXk1khPA+OujTambt3Z4sPzXbnbB5W3xUKMJIxYACileMq2JOIMNTVVNIUktcRXjrYpj7IkGQYoZlEWpnKf2DFVGFxY9KeMGalZBpkyYDG3+zEsR2lWw69I3zipkSfLmbMuUi9gTGV0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jul 02, 2026 at 10:05:48AM +0200, David Hildenbrand (Arm) wrote: > On 7/2/26 01:59, Barry Song (Xiaomi) wrote: > > There is a case where `folio_ref_count(folio) == 3` and > > `!folio_test_swapcache(folio)`. In that case, both > > `folio_ref_count(folio) > 3` and > > `folio_ref_count(folio) > 1 + folio_test_swapcache(folio)` evaluate > > false, causing an unnecessary local LRU drain. > > > > During an Ubuntu boot, I observed over 5,000 redundant local LRU > > drains. For a kernel build with a minimal configuration, I observed > > more than 20,000 redundant drains. > > > > Fix this by checking against: `1 + in_swapcache + in_lrucache` > > instead of hardcoding `folio_ref_count(folio) > 3`. > > > > Suggested-by: David Hildenbrand (Arm) > > Reviewed-by: Kairui Song > > Acked-by: Shakeel Butt > > Reviewed-by: Baoquan He > > Signed-off-by: Barry Song (Xiaomi) > > --- > The other folks should probably re-review this patch that changed quite a bit :) > > > Acked-by: David Hildenbrand (Arm) The code looks much better and Barry can keep my tag.