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[129.46.96.20]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7d59785d8d5sm9311790a34.17.2026.03.03.03.30.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Mar 2026 03:30:34 -0800 (PST) From: Yuvraj Sakshith To: mst@redhat.com, david@kernel.org Cc: 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, akpm@linux-foundation.org, 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, linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, linux-mm@kvack.org Subject: [PATCH v4 0/5] Allow order zero pages in page reporting Date: Tue, 3 Mar 2026 03:30:27 -0800 Message-Id: <20260303113032.3008371-1-yuvraj.sakshith@oss.qualcomm.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzAzMDA4OSBTYWx0ZWRfX4wjRGG0GsW2k MdPc6t/OVPUUVXJGL8pslQpp2z06y3AZALM/lnNCDBNdGQw2HNUfIHi4YIut7FE0IpS69pHpDlt qI75JPS/pSrTvU9TNtrPxeTz4GbJLZkm1f3IE7m+KGtlJxmJJtb2Q6/zezx/BpFCEdz4v8geYdQ wA9CGzvNYwOgrfnD6ejMxdIe7znQUvMZJUKyFXeJTBYPc7tO+AArmw2iwB8HznNiSOcPW7kdf4o QlvPZUHI0G1d47a6jg0U8Ce7UnSpVoo+WIOF2UOrAgzecxQs6xKn72LXC6GMvZHOp55zitr767N GG3gIMpYN09zyi+8vnIJ8z4Qt4DkRLiKabLwu1VXH9li8J0AoWSX1+HBryEK3IG1RnRMk6xx06k VRpX7klzpsF1M8riE5U7MrS120zMoqrAPDVgT4LXXtO/V4x1sXBR/sBf6rvq6Xt1ryyQu0aB6ap 0Pj4Q5MAbiZupwozjzw== X-Proofpoint-ORIG-GUID: iDyCgCDf7eSNWYPtQZSbAF84A9reMeGG X-Authority-Analysis: v=2.4 cv=S+HUAYsP c=1 sm=1 tr=0 ts=69a6c65b cx=c_pps a=7uPEO8VhqeOX8vTJ3z8K6Q==:117 a=ouPCqIW2jiPt+lZRy3xVPw==:17 a=Yq5XynenixoA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=3WHJM1ZQz_JShphwDgj5:22 a=HYTG7BDJ-qdBC1FqdxkA:9 a=EXS-LbY8YePsIyqnH6vw:22 X-Proofpoint-GUID: iDyCgCDf7eSNWYPtQZSbAF84A9reMeGG 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=2026-03-02_05,2026-03-03_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 malwarescore=0 lowpriorityscore=0 bulkscore=0 suspectscore=0 clxscore=1015 spamscore=0 priorityscore=1501 adultscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2602130000 definitions=main-2603030089 X-Rspam-User: X-Rspamd-Queue-Id: CD43B40003 X-Rspamd-Server: rspam08 X-Stat-Signature: hhnkrg6qbaco49u6gff41k3qkod8jazd X-HE-Tag: 1772537436-918618 X-HE-Meta: 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 svbvQaJU 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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. Changes in v2: - Better naming. Replace PAGE_REPORTING_DEFAULT_ORDER with PAGE_REPORTING_ORDER_UNSPECIFIED. This takes care of the situation where page reporting order is not specified in the commandline. - Minor commit message changes. Changes in v3: - Setting page_reporting_order's initial value to PAGE_REPORTING_ORDER_UNSPECIFIED moved to PATCH #5. Changes in v4: - Move PAGE_REPORTING_ORDER_UNSPECIFIED's usage with page_reporting_order to patch #5. Yuvraj Sakshith (5): mm/page_reporting: add PAGE_REPORTING_ORDER_UNSPECIFIED virtio_balloon: set unspecified page reporting order hv_balloon: set unspecified page reporting order mm/page_reporting: change PAGE_REPORTING_ORDER_UNSPECIFIED to -1 mm/page_reporting: change page_reporting_order to PAGE_REPORTING_ORDER_UNSPECIFIED drivers/hv/hv_balloon.c | 2 +- drivers/virtio/virtio_balloon.c | 2 ++ include/linux/page_reporting.h | 1 + mm/page_reporting.c | 7 ++++--- 4 files changed, 8 insertions(+), 4 deletions(-) -- 2.34.1