Messages in this thread | | | Date | Mon, 6 Jun 2022 15:46:36 +0530 | Subject | Re: [RFC PATCH v4 4/7] mm/demotion/dax/kmem: Set node's memory tier to MEMORY_TIER_PMEM | From | Aneesh Kumar K V <> |
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On 6/6/22 3:41 PM, Bharata B Rao wrote: > On 6/3/2022 2:34 PM, Aneesh Kumar K V wrote: >> On 6/2/22 12:06 PM, Bharata B Rao wrote: >>> On 6/1/2022 7:19 PM, Aneesh Kumar K V wrote: >>>> On 6/1/22 11:59 AM, Bharata B Rao wrote: >>>>> I was experimenting with this patchset and found this behaviour. >>>>> Here's what I did: >>>>> >>>>> Boot a KVM guest with vNVDIMM device which ends up with device_dax >>>>> driver by default. >>>>> >>>>> Use it as RAM by binding it to dax kmem driver. It now appears as >>>>> RAM with a new NUMA node that is put to memtier1 (the existing tier >>>>> where DRAM already exists) >>>>> >>>> >>>> That should have placed it in memtier2. >>>> >>>>> I can move it to memtier2 (MEMORY_RANK_PMEM) manually, but isn't >>>>> that expected to happen automatically when a node with dax kmem >>>>> device comes up? >>>>> >>>> >>>> This can happen if we have added the same NUMA node to memtier1 before dax kmem driver initialized the pmem memory. Can you check before the above node_set_memory_tier_rank() whether the specific NUMA node is already part of any memory tier? >>> >>> When we reach node_set_memory_tier_rank(), node1 (that has the pmem device) >>> is already part of memtier1 whose nodelist shows 0-1. >>> >> >> can you find out which code path added node1 to memtier1? > > node_set_memory_tier_rank+0x63/0x80 > migrate_on_reclaim_callback+0x40/0x4d > blocking_notifier_call_chain+0x68/0x90 > memory_notify+0x1b/0x20 > online_pages+0x257/0x2f0 > memory_subsys_online+0x99/0x150 > device_online+0x65/0x90 > online_memory_block+0x1b/0x20 > walk_memory_blocks+0x85/0xc0 > ? generic_online_page+0x40/0x40 > add_memory_resource+0x1fa/0x2d0 > add_memory_driver_managed+0x80/0xc0 > dev_dax_kmem_probe+0x1af/0x250 > dax_bus_probe+0x6e/0xa0 > > After this the explicit call to node_set_memory_tier_rank(numa_node, MEMORY_RANK_PMEM) > from dev_dax_kmem_probe() finds that the memtier is already set. > >> Do you have regular memory also appearing on node1? > > No, regular memory is on Node0. >
Thanks for the stack trace. I was getting the kvm setup on my laptop to test this. We should move node_set_mem_tier() early. You had automatic online on memory hotplug
/* online pages if requested */ if (mhp_default_online_type != MMOP_OFFLINE) walk_memory_blocks(start, size, NULL, online_memory_block);
which caused memory to be onlined before we could do node_set_mem_tier. That is a bug on my side. Will send you a change after testing .
-aneesh
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