kernel/git/next/linux-next.git/samples/damon/mtier.c, branch stable

samples/damon/mtier: fail early if address range parameters are invalid

2026-07-02T02:02:56+00:00

The comment on top of `struct damon_region` clearly says that For any use case, @ar should be non-zero positive size. which is now verified in damon_verify_new_region() if the kernel is built with DAMON_DEBUG_SANITY. The WARN_ONCE() can be triggered if the mtier sample module is enabled before node{0,1}_{start,end}_addr have been properly initialized, which is obviously not good. ------------[ cut here ]------------ start 0 >= end 0 WARNING: mm/damon/core.c:217 at damon_new_region+0xf4/0x118, CPU#59: bash/341468 Call trace: damon_new_region+0xf4/0x118 (P) damon_set_regions+0xfc/0x3c0 damon_sample_mtier_build_ctx+0xe8/0x3a8 damon_sample_mtier_start+0x1c/0x90 damon_sample_mtier_enable_store+0x98/0xb0 param_attr_store+0xb4/0x128 module_attr_store+0x2c/0x50 sysfs_kf_write+0x58/0x90 kernfs_fop_write_iter+0x16c/0x238 vfs_write+0x2c0/0x370 ksys_write+0x74/0x118 __arm64_sys_write+0x24/0x38 invoke_syscall+0xa8/0x118 el0_svc_common.constprop.0+0x48/0xf0 do_el0_svc+0x24/0x38 el0_svc+0x54/0x370 el0t_64_sync_handler+0xa0/0xe8 el0t_64_sync+0x1ac/0x1b0 ---[ end trace 0000000000000000 ]--- Note that the same issue can happen if detect_node_addresses is true, and node 0 or 1 is memoryless. Fix it together by checking the validity of parameters right before damon_new_region() and fail early if they're invalid. Link: https://lore.kernel.org/20260629144432.133962-1-sj@kernel.org Fixes: 82a08bde3cf7 ("samples/damon: implement a DAMON module for memory tiering") Signed-off-by: Zenghui Yu Signed-off-by: SJ Park Reviewed-by: SJ Park Cc: # 6.16.x Signed-off-by: Andrew Morton

samples/damon/mtier: replace damon_add_region() with damon_set_regions()

2026-06-04T21:45:00+00:00

mtier DAMON sample module and DAMON virtual address operation set (vaddr) unit tests are using damon_add_region() for setup of DAMON monitoring target region boundaries setup. But, damon_set_regions() is designed for exactly the purpose. All other DAMON API callers use the function for the purpose. Replace damon_add_region() usage in mtier sample module with damon_set_regions(), for unifying the use case and reducing the maintenance cost. Link: https://lore.kernel.org/20260522154026.80546-4-sj@kernel.org Signed-off-by: SeongJae Park Cc: Brendan Higgins Cc: Shuah Khan Signed-off-by: Andrew Morton

samples/damon/mtier: use damon_initialized()

2025-09-21T21:22:39+00:00

damon_sample_mtier is assuming DAMON is ready to use in module_init time, and uses its own hack to see if it is the time. Use damon_initialized(), which is a way for seeing if DAMON is ready to be used that is more reliable and better to maintain instead of the hack. Link: https://lkml.kernel.org/r/20250916033511.116366-8-sj@kernel.org Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton

samples/damon/mtier: avoid starting DAMON before initialization

2025-09-13T20:05:38+00:00

Commit 964314344eab ("samples/damon/mtier: support boot time enable setup") is somehow incompletely applying the origin patch [1]. It is missing the part that avoids starting DAMON before module initialization. Probably a mistake during a merge has happened. Fix it by applying the missed part again. Link: https://lkml.kernel.org/r/20250909022238.2989-4-sj@kernel.org Link: https://lore.kernel.org/20250706193207.39810-4-sj@kernel.org [1] Fixes: 964314344eab ("samples/damon/mtier: support boot time enable setup") Signed-off-by: SeongJae Park Cc: Signed-off-by: Andrew Morton

samples/damon: support automatic node address detection

2025-07-20T01:59:47+00:00

This patch adds a new knob `detect_node_addresses`, which determines whether the physical address range is set manually using the existing knobs or automatically by the mtier module. When `detect_node_addresses` set to 'Y', mtier automatically converts node0 and node1 to their physical addresses. If set to 'N', it uses the existing 'node#_start_addr' and 'node#_end_addr' to define regions as before. Link: https://lkml.kernel.org/r/20250707235919.513-1-yunjeong.mun@sk.com Signed-off-by: Yunjeong Mun Suggested-by: Honggyu Kim Reviewed-by: SeongJae Park Signed-off-by: Andrew Morton

samples/damon: change enable parameters to enabled

2025-07-20T01:59:47+00:00

The damon_{lru_sort,reclaim,stat} kernel modules use "enabled" parameter knobs as follows. /sys/module/damon_lru_sort/parameters/enabled /sys/module/damon_reclaim/parameters/enabled /sys/module/damon_stat/parameters/enabled However, other sample modules of damon use "enable" parameter knobs so it'd be better to rename them from "enable" to "enabled" to keep the consistency with other damon modules. Before: /sys/module/damon_sample_wsse/parameters/enable /sys/module/damon_sample_prcl/parameters/enable /sys/module/damon_sample_mtier/parameters/enable After: /sys/module/damon_sample_wsse/parameters/enabled /sys/module/damon_sample_prcl/parameters/enabled /sys/module/damon_sample_mtier/parameters/enabled There is no functional changes in this patch. Link: https://lkml.kernel.org/r/20250707024548.1964-1-honggyu.kim@sk.com Signed-off-by: Honggyu Kim Reviewed-by: SeongJae Park Signed-off-by: Andrew Morton

samples/damon/mtier: rename to have damon_sample_ prefix

2025-07-20T01:59:43+00:00

DAMON sample module, mtier has its name 'mtier'. It could conflict with future modules, and not very easy to identify it by name. Use a prefix, "damon_sample_" for the name. Note that this could break users if they depend on the old name. But it is just a sample, so no such usage is expected, or known. Even if such usage exists, updating it for the new name should be straightforward. Link: https://lkml.kernel.org/r/20250705175000.56259-4-sj@kernel.org Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton

samples/damon/mtier: support boot time enable setup

2025-07-13T23:38:34+00:00

If 'enable' parameter of the 'mtier' DAMON sample module is set at boot time via the kernel command line, memory allocation is tried before the slab is initialized. As a result kernel NULL pointer dereference BUG can happen. Fix it by checking the initialization status. Link: https://lkml.kernel.org/r/20250706193207.39810-4-sj@kernel.org Fixes: 82a08bde3cf7 ("samples/damon: implement a DAMON module for memory tiering") Signed-off-by: SeongJae Park Cc: Signed-off-by: Andrew Morton

samples/damon/mtier: add parameters for node0 memory usage

2025-07-13T23:38:19+00:00

Change the hard-coded quota goal metric values into sysfs knobs: `node0_mem_used_bp` and `node0_mem_free_bp`. These knobs represent the used and free memory ratio of node0 in basis points (bp, where 1 bp = 0.01%). As mentioned in [1], this patch is developed under the assumption that node0 is always the fast-tier in a two-tiers memory setup. [1] https://lore.kernel.org/linux-mm/20250420194030.75838-8-sj@kernel.org/ Link: https://lkml.kernel.org/r/20250627163329.50997-1-sj@kernel.org Link: https://patch.msgid.link/20250619050313.1535-1-yunjeong.mun@sk.com Signed-off-by: Yunjeong Mun Signed-off-by: SeongJae Park Suggested-by: Honggyu Kim Reviewed-by: SeongJae Park Signed-off-by: Andrew Morton

samples/damon: fix damon sample mtier for start failure

2025-07-10T04:07:55+00:00

The damon_sample_mtier_start() can fail so we must reset the "enable" parameter to "false" again for proper rollback. In such cases, setting Y to "enable" then N triggers the similar crash with mtier because damon sample start failed but the "enable" stays as Y. Link: https://lkml.kernel.org/r/20250702000205.1921-4-honggyu.kim@sk.com Fixes: 82a08bde3cf7 ("samples/damon: implement a DAMON module for memory tiering") Signed-off-by: Honggyu Kim Reviewed-by: SeongJae Park Cc: Signed-off-by: Andrew Morton