From: Li Zhijian <lizhijian@fujitsu.com> mainline inclusion from mainline-v6.9-rc1 commit 601e793a749d6798764cd2eb7f459452f971ee61 category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/9812 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... ------------------------------------------- Currently, when a demotion occurs, it will prioritize selecting a node from the preferred targets as the destination node for the demotion. If the preferred node does not meet the requirements, it will try from all the lower memory tier nodes until it finds a suitable demotion destination node or ultimately fails. However, the demotion target information isn't exposed to the users, especially the preferred target information, which relies on more factors. This makes it hard for users to understand the exact demotion behavior. Rather than having a new sysfs interface to expose this information, printing directly to kernel messages, just like the current page allocation fallback order does. A dmesg example with this patch is as follows: [ 0.704860] Demotion targets for Node 0: null [ 0.705456] Demotion targets for Node 1: null // node 2 is onlined [ 32.259775] Demotion targets for Node 0: perferred: 2, fallback: 2 [ 32.261290] Demotion targets for Node 1: perferred: 2, fallback: 2 [ 32.262726] Demotion targets for Node 2: null // node 3 is onlined [ 42.448809] Demotion targets for Node 0: perferred: 2, fallback: 2-3 [ 42.450704] Demotion targets for Node 1: perferred: 2, fallback: 2-3 [ 42.452556] Demotion targets for Node 2: perferred: 3, fallback: 3 [ 42.454136] Demotion targets for Node 3: null // node 4 is onlined [ 52.676833] Demotion targets for Node 0: perferred: 2, fallback: 2-4 [ 52.678735] Demotion targets for Node 1: perferred: 2, fallback: 2-4 [ 52.680493] Demotion targets for Node 2: perferred: 4, fallback: 3-4 [ 52.682154] Demotion targets for Node 3: null [ 52.683405] Demotion targets for Node 4: null // node 5 is onlined [ 62.931902] Demotion targets for Node 0: perferred: 2, fallback: 2-5 [ 62.938266] Demotion targets for Node 1: perferred: 5, fallback: 2-5 [ 62.943515] Demotion targets for Node 2: perferred: 4, fallback: 3-4 [ 62.947471] Demotion targets for Node 3: null [ 62.949908] Demotion targets for Node 4: null [ 62.952137] Demotion targets for Node 5: perferred: 3, fallback: 3-4 Regarding this requirement, we have previously discussed [1]. The initial proposal involved introducing a new sysfs interface. However, due to concerns about potential changes and compatibility issues with the interface in the future, a consensus was not reached with the community. Therefore, this time, we are directly printing out the information. [1] https://lore.kernel.org/all/d1d5add8-8f4a-4578-8bf0-2cbe79b09989@fujitsu.com... Link: https://lkml.kernel.org/r/20240206020151.605516-1-lizhijian@fujitsu.com Signed-off-by: Li Zhijian <lizhijian@fujitsu.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com> --- mm/memory-tiers.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c index 0ec9ea04375a..393f91e665f3 100644 --- a/mm/memory-tiers.c +++ b/mm/memory-tiers.c @@ -378,6 +378,26 @@ static void disable_all_demotion_targets(void) synchronize_rcu(); } +static void dump_demotion_targets(void) +{ + int node; + + for_each_node_state(node, N_MEMORY) { + struct memory_tier *memtier = __node_get_memory_tier(node); + nodemask_t preferred = node_demotion[node].preferred; + + if (!memtier) + continue; + + if (nodes_empty(preferred)) + pr_info("Demotion targets for Node %d: null\n", node); + else + pr_info("Demotion targets for Node %d: preferred: %*pbl, fallback: %*pbl\n", + node, nodemask_pr_args(&preferred), + nodemask_pr_args(&memtier->lower_tier_mask)); + } +} + /* * Find an automatic demotion target for all memory * nodes. Failing here is OK. It might just indicate @@ -462,7 +482,7 @@ static void establish_demotion_targets(void) * Now build the lower_tier mask for each node collecting node mask from * all memory tier below it. This allows us to fallback demotion page * allocation to a set of nodes that is closer the above selected - * perferred node. + * preferred node. */ lower_tier = node_states[N_MEMORY]; list_for_each_entry(memtier, &memory_tiers, list) { @@ -475,6 +495,8 @@ static void establish_demotion_targets(void) nodes_andnot(lower_tier, lower_tier, tier_nodes); memtier->lower_tier_mask = lower_tier; } + + dump_demotion_targets(); } #else -- 2.43.0