From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CB048FCB602 for ; Fri, 6 Mar 2026 14:44:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=rVOuRHzbb78rDghmOzdwXp0BBGM5x6oDTSHJ79QBAbE=; b=Qr/tyejZgyaxxWEeZbt+WioBBT 1srIYl0aAfKfDDEc7yhp8U5Kd19y3O2p4tBUVObHQOH1/NonVXD4LEMrqErbrNna90ISD53AUdjy/ 8yNTZ9VVvC30btnmIr/MYbtayH5Shwl+cHUH8RsFJUyRT8bG0WQ3jR0COSukDuTzXTnQHR0hZlb47 BLpGduGX1vr0QvApoOHmztqobnW2fqziHimfZGkbtpU7c+U9ZpBqKWG91jNHm0ZGMI1bQWcJBb3pv d1fDnUKeihYzFbPGVbTtkb2IpXZSsclPy22ykQYr32IO5XMKTQIs1w8x56GKio/Duvbc0qowqJqGa /LHyJ7/g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vyWPs-00000003xwc-3GO0; Fri, 06 Mar 2026 14:44:36 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vyWPq-00000003xvh-3bO1 for linux-arm-kernel@lists.infradead.org; Fri, 06 Mar 2026 14:44:35 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 2623A40AA2; Fri, 6 Mar 2026 14:44:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 558F2C4CEF7; Fri, 6 Mar 2026 14:44:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772808274; bh=h+9NOHTHb670Zu/LaAQoajYcmVO5KayLeLmuYtsBpI8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=s5IavVUMaXkrwKQN2iEP03w/Ma20tNYqh5/cw7vFEa3F2Yzq0z8E64Db5UxXuXLWU SV3VAt3ex/Ny8k60RFhUmy/PSSZOBqxCKUvsAWOIlmbs61bdWP1x0n39RoHRnXsAUf hO14BWZmF2RwY7umyNLWacoxeGw9KmZTAmliY0f82LjFe1W+9Tl8W4O6v3lLc11x6f VwwjkElBr4tn40lpGnbCfZh18u2CTYg67SxqPKwMgUOerITGkyJjJe1cQenHbw9cEt r6NZnhNlstCYXoBs04er4pNstLade/z245MgEOUqrmEDkvQNHpZkwjIzgavqLPw9Zb baZZX52Hb10Yg== Message-ID: Date: Fri, 6 Mar 2026 15:44:23 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 5/6] mm: support batched checking of the young flag for MGLRU To: Baolin Wang , akpm@linux-foundation.org Cc: catalin.marinas@arm.com, will@kernel.org, lorenzo.stoakes@oracle.com, ryan.roberts@arm.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, riel@surriel.com, harry.yoo@oracle.com, jannh@google.com, willy@infradead.org, baohua@kernel.org, dev.jain@arm.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, hannes@cmpxchg.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <378f4acf7d07410aa7c2e4b49d56bb165918eb34.1772778858.git.baolin.wang@linux.alibaba.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260306_064434_938768_E1862CFC X-CRM114-Status: GOOD ( 17.30 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 3/6/26 07:43, Baolin Wang wrote: > Use the batched helper test_and_clear_young_ptes_notify() to check and clear > the young flag to improve the performance during large folio reclamation when > MGLRU is enabled. > > Meanwhile, we can also support batched checking the young and dirty flag > when MGLRU walks the mm's pagetable to update the folios' generation > counter. Since MGLRU also checks the PTE dirty bit, use folio_pte_batch_flags() > with FPB_MERGE_YOUNG_DIRTY set to detect batches of PTEs for a large folio. > > Then we can remove the ptep_test_and_clear_young_notify() since it has > no users now. > > Note that we also update the 'young' counter and 'mm_stats[MM_LEAF_YOUNG]' > counter with the batched count in the lru_gen_look_around() and walk_pte_range(). > However, the batched operations may inflate these two counters, because in > a large folio not all PTEs may have been accessed. (Additionally, tracking > how many PTEs have been accessed within a large folio is not very meaningful, > since the mm core actually tracks access/dirty on a per-folio basis, not per > page). The impact analysis is as follows: > > 1. The 'mm_stats[MM_LEAF_YOUNG]' counter has no functional impact and is > mainly for debugging. > > 2. The 'young' counter is used to decide whether to place the current PMD > entry into the bloom filters by suitable_to_scan() (so that next time we > can check whether it has been accessed again), which may set the hash bit > in the bloom filters for a PMD entry that hasn’t seen much access. However, > bloom filters inherently allow some error, so this effect appears negligible. > > Reviewed-by: Rik van Riel > Signed-off-by: Baolin Wang > --- Thanks! Acked-by: David Hildenbrand (Arm) -- Cheers, David