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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shakeel Butt , Mathieu Desnoyers , , , , Nirmoy Das Subject: [RFC PATCH] mm: use precise current RSS for high-water accounting Date: Thu, 23 Jul 2026 06:41:58 -0700 Message-ID: <20260723134158.1473841-1-nirmoyd@nvidia.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.126.230.37] X-ClientProxiedBy: rnnvmail201.nvidia.com (10.129.68.8) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN1PEPF000397B4:EE_|CY8PR12MB7170:EE_ X-MS-Office365-Filtering-Correlation-Id: 40f3c0cb-e3ca-4e5d-a225-08dee8c047f4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|36860700016|376014|7416014|1800799024|82310400026|10067099003|11063799006|18002099003|56012099006; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.117.160;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge1.nvidia.com;CAT:NONE;SFS:(13230040)(23010399003)(36860700016)(376014)(7416014)(1800799024)(82310400026)(10067099003)(11063799006)(18002099003)(56012099006);DIR:OUT;SFP:1101; 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On large systems, this can under-report the current RSS used for high-water accounting. On a 352-CPU, 2-node system with 64 KiB pages, reproduce with: sudo -E env LTPROOT=/opt/ltp \ PATH=/opt/ltp/testcases/bin:$PATH LTP_TIMEOUT_MUL=5 \ bash -c "cd /opt/ltp/testcases/bin && ./getrusage03" The test failed 10/10 times with child.children=270336 instead of 307200. Use get_mm_rss_sum() when reading and resetting high-water RSS. Keep update_hiwater_rss() on the approximate path because it runs before RSS-decreasing operations. The patched kernel passed getrusage03 20/20 times. getrusage01, getrusage02 and getrusage04 also passed. Fixes: f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter") Cc: stable@vger.kernel.org Assisted-by: Cursor:claude-opus-4-8-thinking-max Signed-off-by: Nirmoy Das --- include/linux/mm.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 485df9c2dbddb..1b613c6356baa 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3405,7 +3405,7 @@ static inline unsigned long get_mm_rss_sum(struct mm_struct *mm) static inline unsigned long get_mm_hiwater_rss(struct mm_struct *mm) { - return max(mm->hiwater_rss, get_mm_rss(mm)); + return max(mm->hiwater_rss, get_mm_rss_sum(mm)); } static inline unsigned long get_mm_hiwater_vm(struct mm_struct *mm) @@ -3429,7 +3429,7 @@ static inline void update_hiwater_vm(struct mm_struct *mm) static inline void reset_mm_hiwater_rss(struct mm_struct *mm) { - mm->hiwater_rss = get_mm_rss(mm); + mm->hiwater_rss = get_mm_rss_sum(mm); } static inline void setmax_mm_hiwater_rss(unsigned long *maxrss, base-commit: 4539944e515183668109bdf4d0c3d7d228383d88 -- 2.43.0