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imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=oOAuOjkU; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf13.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1772225053; a=rsa-sha256; cv=none; b=V0SERH22DxvTVKmyPDrqrFF9rJ2iBJ5wtF6cy/EzXg6jlrn2Y4M/7oxhYoLT8HnVrCzopm jN54qoG/KyI6/dWjb7Lv9DTSEsaGWMDwYFS5oufSVX9ta74TmrhSwrTk1zNTky3zPpGG91 6W8RCsX9Wi3zyc6oOMkG/vxK05l4kHM= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 9FCF460126; Fri, 27 Feb 2026 20:44:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9AC9FC116C6; Fri, 27 Feb 2026 20:44:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772225052; bh=RlLz8Nf4AkH8nV2nxyW0Rxk/9bF52X89NSCa8ZhU4q8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=oOAuOjkUW7IMZGQo1i21CTSIVY4JFqKbBBVzBQHEfOB6DW4g3pTxKqT0HrN3xBcST I4yLuWrb/S+kyiwhNBguxN0eQmLjX3Z/9TNeSMmlOAe/9CT2SN+BGGPsFkpm78GRAW wRVFvUOsebWDu+QoYzJqdD5JWZ+35Lix/699e/L9UhApjIJEeWpTbgRc07cXtoVUx2 hgH4I1XJ86b2WoKkXKQOLU203ANhQzMxQU9ktGQFvP0tVqpyPonzdfBMbQnZtsnVW3 G4B64tPdKNSB/D3YARx208WO6SfNSzQ4NWEpyFscgTKv/F5QL4mVmkqe1OTvWIaRih f0rswjD7njamg== Message-ID: Date: Fri, 27 Feb 2026 21:44:05 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 0/4] Allow order zero pages in page reporting To: Yuvraj Sakshith , akpm@linux-foundation.org Cc: mst@redhat.com, kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, longli@microsoft.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, linux-hyperv@vger.kernel.org, virtualization@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260227140655.360696-1-yuvraj.sakshith@oss.qualcomm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 24C8D2000E X-Stat-Signature: ngphstxsr13t9ifyk144doe8b7ygxae5 X-Rspam-User: X-HE-Tag: 1772225052-264951 X-HE-Meta: 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 Wq1u48j7 t8OONIAjTFnT3xrsEwGyI5qQPkpP046ezqetriSMTFIqNGcDgUxT9k5dqUMm0HhdqL14Bn2a47WM4Hsb5cbwGrh32XMyccMZaUTVFiOUrgY92RKwjmba7OrvRiQ6z4pv4K+N25Rt549Ggl8ucrI1/7/oQbYHJeUB8ZmuFxpZfphRwCxkBwjkQqbjwY2UoyCDx/oP7+SUw5LBZj6XaM+MFCs4RAd3LrNzVA0ICz6/Oak+sO5Qvxz2ZhZmVWAu91jKnEa6i+ptaDmxAB1s= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/27/26 15:06, Yuvraj Sakshith wrote: > Today, page reporting sets page_reporting_order in two ways: > > (1) page_reporting.page_reporting_order cmdline parameter > (2) Driver can pass order while registering itself. > > In both cases, order zero is ignored by free page reporting > because it is used to set page_reporting_order to a default > value, like MAX_PAGE_ORDER. > > In some cases we might want page_reporting_order to be zero. > > For instance, when virtio-balloon runs inside a guest with > tiny memory (say, 16MB), it might not be able to find a order 1 page > (or in the worst case order MAX_PAGE_ORDER page) after some uptime. > Page reporting should be able to return order zero pages back for > optimal memory relinquishment. > > This patch changes the default fallback value from '0' to '-1' in > all possible clients of free page reporting (hv_balloon and > virtio-balloon) together with allowing '0' as a valid order in > page_reporting_register(). > > Changes in v1: > - Introduce PAGE_REPORTING_DEFAULT_ORDER macro (initially set to 0). > - Make use of new macro in drivers (hv_balloon and virtio-balloon) > working with page reporting. > - Change PAGE_REPORTING_DEFAULT_ORDER to -1 as zero is a valid > page order that can be requested. > > Yuvraj Sakshith (3): > mm/page_reporting: Allow zero page_reporting_order > hv_balloon: Change default page reporting order > virtio_balloon: Set pr_dev.order to new default These look like old stats :) -- Cheers, David