From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 40C8F4314BC for ; Wed, 29 Jul 2026 12:11:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785327095; cv=none; b=Liwdc9QzyqGA1xxxtqugqOGgjX+01uum096PF3EyIXH+Q+8NlJPK9tu18RF66k02Cyufn48nFtkuVGjMy007nr4xXN24i3vxQmjD1R+KtmrjhXZBG7DGTH7yAmudmMA7x7nUGI6GqISuxwtDMcahU/r8O3R7KdmPHzUcIVbRztU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785327095; c=relaxed/simple; bh=zX1xSo0muCKD7eeqpT4jvy3gEKeg0qJEZwwxpkh4a8M=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OVa0FNcB25nCJtHaJ+vEfmk7Q3TK/OcHiSNOhCdEMN8e5CKNJnSKlr/jemCnXvED+qQL2xDI5qVm9HEnSIr8U/KlX7Fe67aMT4cicyMtmrPpYuFq6PRjIYRTCt2dZp0sw7t8Jm9gowKyTPI2UtcCO0jorMU0kXwsfS0/u55M/cM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GhFoAAhs; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GhFoAAhs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 060A41F000E9; Wed, 29 Jul 2026 12:11:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785327090; bh=uJwQ8kTPh1W4/a3MUlvjgjtvhqULKqgMp25Frxkklaw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=GhFoAAhsAmpS5+ALisTdbEtXrsM6n/XKQYlblpt+7NbLMlJPB70lrmH5CiWZtDnOx OEhHbK6fYEhgWqLzFATRKAAHQ+Sb2GNbVhAxHrqSCKBDNm+swHhINIQ+uNDdat3YYc Xce1g065zsoXDXR0wh/SU49+9KNuuiZhwe/CXphdQ+u4pbtAYaq6FnvGySvw1vtfA7 Uxrs+nOSTQhTsaUjeD6D4QsvxTu11Ot4NCBUD/i0sS/cnZOx9DQhrOZkP16ERnYP/N YqF9O8AtiL7kop7S89wPciJVZY9TrqBnGO5TYX6Ad61NpnHQ/ZJKn3ik/MFawgeKxo WLUJ9m6vkVnMQ== Message-ID: <8f74bd51-11f2-4837-9463-d016444e45cc@kernel.org> Date: Wed, 29 Jul 2026 14:11:26 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v2 2/2] mm: improve large folio reuse for LRU-cached folios To: "Barry Song (Xiaomi)" , akpm@linux-foundation.org, linux-mm@kvack.org, ljs@kernel.org Cc: baolin.wang@linux.alibaba.com, dev.jain@arm.com, lance.yang@linux.dev, liam@infradead.org, linux-kernel@vger.kernel.org, npache@redhat.com, ryan.roberts@arm.com, ziy@nvidia.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com References: <20260709081536.82768-1-baohua@kernel.org> <20260709081536.82768-3-baohua@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/9/26 10:15, Barry Song (Xiaomi) wrote: > Large folios may now reside in the per-CPU LRU cache. Before > attempting to reuse them, drain the local LRU cache, which > can still be beneficial in cases where the folios are likely > to remain in this CPU's LRU cache: > > int main(int argc, char *argv[]) > { > int i; > while (1) { > volatile int *p = mmap(0, SIZE, PROT_READ | PROT_WRITE, > MAP_PRIVATE | MAP_ANONYMOUS, > -1, 0); > for (int i = 0; i < SIZE / sizeof(int); i++) > p[i] = i; > madvise((void *)p, SIZE, MADV_PAGEOUT); > if (!fork()) > _exit(0); > for (int i = 0; i < SIZE / sizeof(int); i++) > p[i] = i; > munmap((void *)p, SIZE); > } > return 0; > } > > Signed-off-by: Barry Song (Xiaomi) > --- > mm/memory.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/mm/memory.c b/mm/memory.c > index 5689b7cff76c..1d08ed5ba99b 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -4136,6 +4136,19 @@ static bool __wp_can_reuse_large_anon_folio(struct folio *folio, > folio_unlock(folio); > } > > + if (folio_may_be_lru_cached(folio) && !folio_test_lru(folio)) { > + if (folio_ref_count(folio) > folio_large_mapcount(folio) + 1) I assume that can just be a "!=". > + return false; > + /* > + * A global LRU drain is too expensive, but a local drain > + * can still be beneficial. For example, large folios that > + * have just been swapped in and fall back from > + * do_swap_page() to do_wp_page() are likely still in this > + * CPU's LRU cache. > + */ Do we really need that comment? It's just the same as we have in wp_can_reuse_anon_folio(). So either drop it or use the same comment. I was wondering whether we could unify some logic with wp_can_reuse_anon_folio(), but the checks are just to different. Apart from that LGTM. I'm sure there are some micro-optimizations to be had, but this here should suffice. -- Cheers, David