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Patch series "mm/damon: advance DAMOS-based LRU sorting". DAMOS_LRU_[DE]PRIO actions were added to DAMOS for more access-aware LRU lists sorting. For simple usage, a specialized kernel module, namely DAMON_LRU_SORT, has also been introduced. After the introduction of the module, DAMON got a few important new features, including the aim-based quota auto-tuning, age tracking, young page filter, and monitoring intervals auto-tuning. Meanwhile, DAMOS-based LRU sorting had no direct updates. Now we show some rooms to advance for DAMOS-based LRU sorting. Firstly, the aim-oriented quota auto-tuning can simplify the LRU sorting parameters tuning. But there is no good auto-tuning target metric for LRU sorting use case. Secondly, the behavior of DAMOS_LRU_[DE]PRIO are not very symmetric. DAMOS_LRU_DEPRIO directly moves the pages to inactive LRU list, while DAMOS_LRU_PRIO only marks the page as accessed, so that the page can not directly but only eventually moved to the active LRU list. Finally, DAMON_LRU_SORT users cannot utilize the modern features that can be useful for them, too. Improve the situation with the following changes. First, introduce a new DAMOS quota auto-tuning target metric for active:inactive memory size ratio. Since LRU sorting is a kind of balancing of active and inactive pages, the active:inactive memory size ratio can be intuitively set. Second, update DAMOS_LRU_[DE]PRIO behaviors to be more intuitive and symmetric, by letting them directly move the pages to [in]active LRU list. Third, update the DAMON_LRU_SORT module user interface to be able to fully utilize the modern features including the [in]active memory size ratio-based quota auto-tuning, young page filter, and monitoring intervals auto-tuning. With these changes, for example, users can now ask DAMON to "find hot/cold memory regions with auto-tuned monitoring intervals, do one more page level access check for found hot/cold memory, and move pages of those to active or inactive LRU lists accordingly, aiming X:Y active to inactive memory ratio." For example, if they know 30% of the memory is better to be protected from reclamation, 30:70 can be set as the target ratio. Test Results ------------ I ran DAMON_LRU_SORT with the features introduced by this series, on a real world server workload. For the active:inactive ratio goal, I set 50:50. I confirmed it achieves the target active:inactive ratio, without manual tuning of the monitoring intervals and the hot/coldness thresholds. The baseline system that was not running the DAMON_LRU_SORT was keeping active:inactive ratio of about 1:10. Note that the test didn't show a clear performance difference, though. I believe that was mainly because the workload was not very memory intensive. Also, whether the 50:50 target ratio was optimum is unclear. Nonetheless, the positive performance impact of the basic LRU sorting idea is already confirmed with the initial DAMON_LRU_SORT introduction patch series. The goal of this patch series is simplifying the parameters tuning of DAMOS-based LRU sorting, and the test confirmed the aimed goals are achieved. Patches Sequence ---------------- First three patches extend DAMOS quota auto-tuning to support [in]active memory ratio target metric type. Those (patches 1-3) introduce new metrics, implement DAMON sysfs support, and update the documentation, respectively. Following patch (patch 4) makes DAMOS_LRU_PRIO action to directly move target pages to active LRU list, instead of only marking them accessed. Following seven patches (patches 5-11) updates DAMON_LRU_SORT to support modern DAMON features. Patch 5 makes it uses not only access frequency but also age at under-quota regions prioritization. Patches 6-11 add the support for young page filtering, active:inactive memory ratio based quota auto-tuning, and monitoring intervals auto-tuning, with appropriate document updates. This patch (of 11): DAMOS_LRU_[DE]PRIO are DAMOS actions for making balance of active and inactive memory size. There is no appropriate DAMOS quota auto-tuning target metric for the use case. Add two new DAMOS quota goal metrics for the purpose, namely DAMOS_QUOTA_[IN]ACTIVE_MEM_BP. Those will represent the ratio of [in]active memory to total (inactive + active) memory. Hence, users will be able to ask DAMON to, for example, "find hot and cold memory, and move pages of those to active and inactive LRU lists, adjusting the hot/cold thresholds aiming 50:50 active:inactive memory ratio." Link: https://lkml.kernel.org/r/20260113152717.70459-1-sj@kernel.org Link: https://lkml.kernel.org/r/20260113152717.70459-2-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: David Hildenbrand <david@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst