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[129.46.96.20]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7d5866269a8sm4324502a34.13.2026.02.27.06.06.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Feb 2026 06:06:57 -0800 (PST) From: Yuvraj Sakshith To: akpm@linux-foundation.org Cc: mst@redhat.com, david@kernel.org, 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 Subject: [PATCH v1 0/4] Allow order zero pages in page reporting Date: Fri, 27 Feb 2026 06:06:51 -0800 Message-Id: <20260227140655.360696-1-yuvraj.sakshith@oss.qualcomm.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Authority-Analysis: v=2.4 cv=BOC+bVQG c=1 sm=1 tr=0 ts=69a1a505 cx=c_pps a=7uPEO8VhqeOX8vTJ3z8K6Q==:117 a=ouPCqIW2jiPt+lZRy3xVPw==:17 a=HzLeVaNsDn8A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=ZpdpYltYx_vBUK5n70dp:22 a=9ecvtSpfVrh-a2M179QA:9 a=EXS-LbY8YePsIyqnH6vw:22 X-Proofpoint-GUID: wQ7pTSAsmtjR2lrzlAdZdrf_bp84fSkq X-Proofpoint-ORIG-GUID: wQ7pTSAsmtjR2lrzlAdZdrf_bp84fSkq X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjI3MDEyNSBTYWx0ZWRfX2+iNrIelDZFU lf/XbmtXKVMQv7q6kEO1tJ8sBJwGnZW3ybiS+dya5niBONhnkzIyP3sywoe+5Bz28eQ3uJyrc+A rBJZdZNCLvC9j2Sfb68vK6cROBUJMd6mem2QLjLsCOeEA+j7Y1WGUUll6a+sONOLAautIDK7Dl2 wP0oQ65d4om4CUS2rcce24+n0mAhl+SpwSWaE/O2xVjax4orl3toUmeZPkkH7nMiyj0bFniFQ0g AgYSpl808yG6cZqZrmpH8fct/dBxfaO7tl8NZBkab2iuDGrbgYXImjajJSW2JhOAI/jstacVkCn mJyvKgYTTDA00WfXojXfWkQKdPMmfsuQSATNxfaMfGQev/EnlrkkNL3/NbACU9Il6VEBL905kuB xCSBuz1veXcuC4FcNpKAAY/3Z35EmFTMxW8dPtX4CzVTSjJNRLUU2hMWsVcgCqIZAkJq2+Q0LSS fAvIvC7rqU0Y1dt4Uhw== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-27_02,2026-02-27_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 impostorscore=0 spamscore=0 suspectscore=0 phishscore=0 clxscore=1015 priorityscore=1501 lowpriorityscore=0 adultscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2602130000 definitions=main-2602270125 X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 7AF3318000D X-Stat-Signature: jf9h9fnpi4rirpcd4ad4f75q4rx4ksex X-HE-Tag: 1772201222-835262 X-HE-Meta: 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 uMN5jYWP 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 drivers/hv/hv_balloon.c | 2 +- drivers/virtio/virtio_balloon.c | 14 ++++++++++++++ mm/page_reporting.c | 2 +- 3 files changed, 16 insertions(+), 2 deletions(-) -- 2.34.1