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AHgh+Rr+QH1/Dx2fktpChbnlI0GUM7muR4x+jOLXNq6ozPU6MqhIVIsEZ+veXDFqfkf07+ENLfWqWNmIdQ==@kvack.org X-Gm-Message-State: AOJu0YzPKohlROUszbNc5maaGbwA/ND1CaEKQeYVGM35VsVQ/lLr0nDh EsQWHbKpL9a7H/IGA696LcEtdBqJUVq1BQnAwxxLDYeIULKbZrckQEzgu5aGxV+D3rMcbEXVO1J jqvyY8NagUg== X-Received: from dybb18.prod.google.com ([2002:a05:693c:6092:b0:311:cbf9:7438]) (user=pratmal job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:7007:b0:3c6:3c5b:f2e4 with SMTP id adf61e73a8af0-3c92a8f460fmr957909637.60.1785526627519; Fri, 31 Jul 2026 12:37:07 -0700 (PDT) Date: Fri, 31 Jul 2026 19:37:05 +0000 Mime-Version: 1.0 X-Mailer: git-send-email 2.55.0.508.g3f0d502094-goog Message-ID: <20260731193705.2902728-1-pratmal@google.com> Subject: [PATCH v4] mm/page_reporting: Add page_reporting_delay_ms module parameter From: pratmal@google.com To: akpm@linux-foundation.org, vbabka@kernel.org, david@kernel.org, sj@kernel.org, corbet@lwn.net, ljs@kernel.org Cc: 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, Pratyush Mallick Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 2067820010 X-Stat-Signature: 3zg5n3fwn4e8o9rnb6e53yz6mifginym X-HE-Tag: 1785526629-732296 X-HE-Meta: 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 kpfoW2/p 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Pratyush Mallick Free page reporting currently hardcodes a 2-second interval between reports. This rigid delay cannot accommodate diverse guest workloads. This patch introduces a module parameter, page_reporting_delay_ms (default: 2000), allowing users to tune the reporting rate: - Lower values enable aggressive memory reclamation by returning unused pages to the host immediately. - Higher values help batch pages during spiky allocation/free churn, reducing hypercalls and nested page fault overheads. Setting the delay to 0 is safe and execution is strictly gated by: - reporting is only triggered by high-order page frees. - expensive hypercalls are bounded by a slot capacity watermark check before proceeding. Signed-off-by: Pratyush Mallick --- v4: - Added a helper function for schedule_delayed_work(). - Updated the commit message. - v3: https://lore.kernel.org/linux-mm/amiPTPKfTOEpgetH@lucifer/T/#t v3: - Converted page_reporting_delay_ms from a sysctl to a module parameter. - Dropped the max value cap (PAGE_REPORTING_DELAY_MS_MAX). - Documented page_reporting.page_reporting_delay_ms in Documentation/admin-guide/kernel-parameters.txt. - Updated code comments in mm/page_reporting.c to reflect dynamic parameterization. - v2: https://lore.kernel.org/linux-mm/3da27fde-25dc-4cb8-8e05-74cd26fc2f7c@kernel.org/T/#t v2: - Documented page_reporting_delay_ms in Documentation/admin-guide/sysctl/vm.rst. - v1: https://lore.kernel.org/linux-mm/20260722192935.1646848-1-pratmal@google.com/T/#u v1: Fixed feedback from RFC. - Added lower and upper cap to sysctl value. - Reverted the reordering on page_reporting_delay_ms. - Dropped the mod_delayed_work() change. - RFC: https://lore.kernel.org/linux-mm/20260714171456.2350037-1-pratmal@google.com/T/#u .../admin-guide/kernel-parameters.txt | 6 +++++ mm/page_reporting.c | 26 +++++++++++++------ 2 files changed, 24 insertions(+), 8 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index b5493a7f8f22..364c2dce8e70 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4810,6 +4810,12 @@ Kernel parameters Adjust the minimal page reporting order. The page reporting is disabled when it exceeds MAX_PAGE_ORDER. + page_reporting.page_reporting_delay_ms= + [KNL] Free page reporting delay in milliseconds + Format: + Adjust the delay in milliseconds between free page + reporting intervals. Default is 2000 (2 seconds). + panic= [KNL] Kernel behaviour on panic: delay timeout > 0: seconds before rebooting timeout = 0: wait forever diff --git a/mm/page_reporting.c b/mm/page_reporting.c index 942e84b6908a..c01aa3af80f3 100644 --- a/mm/page_reporting.c +++ b/mm/page_reporting.c @@ -47,7 +47,11 @@ MODULE_PARM_DESC(page_reporting_order, "Set page reporting order"); */ EXPORT_SYMBOL_GPL(page_reporting_order); -#define PAGE_REPORTING_DELAY (2 * HZ) +static unsigned int page_reporting_delay_ms = 2 * MSEC_PER_SEC; +module_param(page_reporting_delay_ms, uint, 0644); +MODULE_PARM_DESC(page_reporting_delay_ms, + "Set page reporting delay in milliseconds"); + static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly; enum { @@ -56,6 +60,13 @@ enum { PAGE_REPORTING_ACTIVE }; +/* schedule work for page reporting */ +static void page_reporting_schedule_work(struct page_reporting_dev_info *prdev) +{ + schedule_delayed_work(&prdev->work, + msecs_to_jiffies(page_reporting_delay_ms)); +} + /* request page reporting */ static void __page_reporting_request(struct page_reporting_dev_info *prdev) @@ -76,11 +87,10 @@ __page_reporting_request(struct page_reporting_dev_info *prdev) return; /* - * Delay the start of work to allow a sizable queue to build. For - * now we are limiting this to running no more than once every - * couple of seconds. + * Delay the start of work to allow a sizable queue to build. + * We limit this based on page_reporting_delay_ms. */ - schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY); + page_reporting_schedule_work(prdev); } /* notify prdev of free page reporting request */ @@ -335,12 +345,12 @@ static void page_reporting_process(struct work_struct *work) err_out: /* * If the state has reverted back to requested then there may be - * additional pages to be processed. We will defer for 2s to allow - * more pages to accumulate. + * additional pages to be processed. We will defer by + * page_reporting_delay_ms to allow more pages to accumulate. */ state = atomic_cmpxchg(&prdev->state, state, PAGE_REPORTING_IDLE); if (state == PAGE_REPORTING_REQUESTED) - schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY); + page_reporting_schedule_work(prdev); } static DEFINE_MUTEX(page_reporting_mutex); -- 2.55.0.508.g3f0d502094-goog