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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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1acb7ba0-6aff-4d30-9554-283ac8fbc93f@kernel.org> X-Stat-Signature: etk4gb6mhzzmorxzrdzixh9458hmn17k X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: B302120007 X-Rspam-User: X-HE-Tag: 1785415426-249462 X-HE-Meta: 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 8u7jCLLP /yI/aSsPSUhY+i/5Kk/IxaJIwZRuOKL5StRq5woyraJPz2+WadtfHm+tP4TLVzbpaOxiLEjo6a9EFqyoNsqr8oPdRzuag8p2qtPoqew/NNBM2YgnZxrLx6CC7yHACP0bDB8zEsVqdBWhpBkkizh/WXQvyrCyEUtmU8aXQjVaF9MCwgonuioAYEOAeHQ1d5X363Yc0FiV15t+HH/I+HCrowVmZsq3GphQkpyCp5QdXpx92rQGjsCK3d3hqCexISw0csxi1LbX3wdoFtp/8Sp/nqy5asiRHa6yOTJJRlWDixpkpsbA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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