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 2869D7262E; Thu, 30 Jul 2026 12:43:45 +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=1785415427; cv=none; b=DbcAOg3zOJPnFaAVmkyWgfYgzTLRDmLFB4sZCY2+Fipl8Gw3OSNcIcf+2w7txiq9vh8RiY35Ovc3kNoycCoxOJV10ghJ3CaecCRhDVr8XqsiIq+plPY/k6uHHPgiEXP+1s/qV2WImGXTPEy17sM+TCe1578W5SZKF/vTbD1bgUU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785415427; c=relaxed/simple; bh=denYXxuZUIjJ7qR+ENW+Wes0wn305emtnulRUupokHM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=M1lf+BXz70azfa3nEaBvCU06MRyv1+GDOHzzxCMV4S3NjkhOImNtN6DfmM+auilP2Yzhaii8QOcHu/2FIgc66NhMw5+dCFzU030pkPL4lDx6ttLg/UZOjcdBlVmBzH9SjhfhE0Niyv1acJHQ1o/stVjGSZJyCSmhu7jeipkOOgw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Xn9CZZ8q; 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="Xn9CZZ8q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F5C61F000E9; Thu, 30 Jul 2026 12:43:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785415425; bh=tv01v+1vmyL2V9Dx2V8kfjj44VgJjpaRsjpUKiXaIwo=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Xn9CZZ8q4fyaTzyVghjcX4coSwOOVxWYub2DQbQTTQ/7S+qjSTdRqwH7KxQN8sA4G KbeBl23oUkUtQxmG5FJgjXHQ5qvuwcrbqSNryM965phjrb42pbs17xhPT9Cipdn1sE sG79Xp1VqF+sUGHLL4At+wPzmS6nTcw5zF8i2/BOpJmfOCZZcjmCiiBsM1reMlMYnw cHp9h8IV3A5IENrcouFOw7G1c4VmJ04YWp6EXWzBFgMUQOqYkIy34herfhc4bamJVv 9i9uRpeu8Jw6sbmqXg04pzmRpAyFUZWoVzNkLhy3yKLRil3Izxoux3cLdlE9Qf9GzT uq6CE9TWqI4nQ== Date: Thu, 30 Jul 2026 13:43:26 +0100 From: "Lorenzo Stoakes (ARM)" To: "David Hildenbrand (Arm)" Cc: Pratyush Mallick , akpm@linux-foundation.org, vbabka@kernel.org, sj@kernel.org, corbet@lwn.net, skhan@linuxfoundation.org, anshuman.khandual@arm.com, gthelen@google.com, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, liam@infradead.org, rppt@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCH v3] mm/page_reporting: Add page_reporting_delay_ms module parameter Message-ID: References: <20260727230545.262579-1-pratmal@google.com> <91b61f02-c533-41b9-b680-7de52a5c6918@kernel.org> <1acb7ba0-6aff-4d30-9554-283ac8fbc93f@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1acb7ba0-6aff-4d30-9554-283ac8fbc93f@kernel.org> On Thu, Jul 30, 2026 at 02:39:51PM +0200, David Hildenbrand (Arm) wrote: > >>> With 2s, we wait 2s before we start reporting immediately by kicking the > >>> workqueue immediately. > >>> > >>> So "0" does not mean "report all the time", rather "start reporting immediately > >>> as we are notified about a pageblock to report". > > > > No, it's whenever pageblock_order is specified, defaulting to a pageblock. > > > > But I guess in practice fine. > > > > There's fun like this in virtio_balloon.c btw: > > > > /* > > * The default page reporting order is @pageblock_order, which > > * corresponds to 512MB in size on ARM64 when 64KB base page > > * size is used. The page reporting won't be triggered if the > > * freeing page can't come up with a free area like that huge. > > * So we specify the page reporting order to 5, corresponding > > * to 2MB. It helps to avoid THP splitting if 4KB base page > > * size is used by host. > > * > > * Ideally, the page reporting order is selected based on the > > * host's base page size. However, it needs more work to report > > * that value. The hard-coded order would be fine currently. > > */ > > #if defined(CONFIG_ARM64) && defined(CONFIG_ARM64_64K_PAGES) > > vb->pr_dev_info.order = 5; > > #endif > > Yes, it's really about "a large chunk of memory was freed". On 64k " a large > chunk" is unfortunately order 5 == 2MiB (so the same as on 4k where a pageblock > is 2M). Yup :) Yeah in general I'm fine then with the timeout being 0, the fact it's batched like this makes that rather moot! > > -- > Cheers, > > David Cheers, Lorenzo