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  1. 06 May, 2024 2 commits
    • Ho-Ren (Jack) Chuang's avatar
      memory tier: create CPUless memory tiers after obtaining HMAT info · cf93be18
      Ho-Ren (Jack) Chuang authored 
      The current implementation treats emulated memory devices, such as CXL1.1
type3 memory, as normal DRAM when they are emulated as normal memory
(E820_TYPE_RAM).  However, these emulated devices have different
characteristics than traditional DRAM, making it important to distinguish
them.  Thus, we modify the tiered memory initialization process to
introduce a delay specifically for CPUless NUMA nodes.  This delay ensures
that the memory tier initialization for these nodes is deferred until HMAT
information is obtained during the boot process.  Finally, demotion tables
are recalculated at the end.

* late_initcall(memory_tier_late_init);
  Some device drivers may have initialized memory tiers between
  `memory_tier_init()` and `memory_tier_late_init()`, potentially bringing
  online memory nodes and configuring memory tiers.  They should be
  excluded in the late init.

* Handle cases where there is no HMAT when creating memory tiers
  There is a scenario where a CPUless node does not provide HMAT
  information.  If no HMAT is specified, it falls back to using the
  default DRAM tier.

* Introduce another new lock `default_dram_perf_lock` for adist
  calculation In the current implementation, iterating through CPUlist
  nodes requires holding the `memory_tier_lock`.  However,
  `mt_calc_adistance()` will end up trying to acquire the same lock,
  leading to a potential deadlock.  Therefore, we propose introducing a
  standalone `default_dram_perf_lock` to protect `default_dram_perf_*`. 
  This approach not only avoids deadlock but also prevents holding a large
  lock simultaneously.

* Upgrade `set_node_memory_tier` to support additional cases, including
  default DRAM, late CPUless, and hot-plugged initializations.  To cover
  hot-plugged memory nodes, `mt_calc_adistance()` and
  `mt_find_alloc_memory_type()` are moved into `set_node_memory_tier()` to
  handle cases where memtype is not initialized and where HMAT information
  is available.

* Introduce `default_memory_types` for those memory types that are not
  initialized by device drivers.  Because late initialized memory and
  default DRAM memory need to be managed, a default memory type is created
  for storing all memory types that are not initialized by device drivers
  and as a fallback.

Link: https://lkml.kernel.org/r/20240405000707.2670063-3-horenchuang@bytedance.comSigned-off-by: default avatarHo-Ren (Jack) Chuang <horenchuang@bytedance.com>
Signed-off-by: default avatarHao Xiang <hao.xiang@bytedance.com>
Reviewed-by: default avatar"Huang, Ying" <ying.huang@intel.com>
Reviewed-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Gregory Price <gourry.memverge@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Ravi Jonnalagadda <ravis.opensrc@micron.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawie.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      cf93be18
    • Ho-Ren (Jack) Chuang's avatar
      memory tier: dax/kmem: introduce an abstract layer for finding, allocating,... · a72a30af
      Ho-Ren (Jack) Chuang authored 
      memory tier: dax/kmem: introduce an abstract layer for finding, allocating, and putting memory types

Patch series "Improved Memory Tier Creation for CPUless NUMA Nodes", v11.

When a memory device, such as CXL1.1 type3 memory, is emulated as normal
memory (E820_TYPE_RAM), the memory device is indistinguishable from normal
DRAM in terms of memory tiering with the current implementation.  The
current memory tiering assigns all detected normal memory nodes to the
same DRAM tier.  This results in normal memory devices with different
attributions being unable to be assigned to the correct memory tier,
leading to the inability to migrate pages between different types of
memory. 
https://lore.kernel.org/linux-mm/PH0PR08MB7955E9F08CCB64F23963B5C3A860A@PH0PR08MB7955.namprd08.prod.outlook.com/T/

This patchset automatically resolves the issues.  It delays the
initialization of memory tiers for CPUless NUMA nodes until they obtain
HMAT information and after all devices are initialized at boot time,
eliminating the need for user intervention.  If no HMAT is specified, it
falls back to using `default_dram_type`.

Example usecase:
We have CXL memory on the host, and we create VMs with a new system memory
device backed by host CXL memory.  We inject CXL memory performance
attributes through QEMU, and the guest now sees memory nodes with
performance attributes in HMAT.  With this change, we enable the guest
kernel to construct the correct memory tiering for the memory nodes.


This patch (of 2):

Since different memory devices require finding, allocating, and putting
memory types, these common steps are abstracted in this patch, enhancing
the scalability and conciseness of the code.

Link: https://lkml.kernel.org/r/20240405000707.2670063-1-horenchuang@bytedance.com
Link: https://lkml.kernel.org/r/20240405000707.2670063-2-horenchuang@bytedance.comSigned-off-by: default avatarHo-Ren (Jack) Chuang <horenchuang@bytedance.com>
Reviewed-by: default avatar"Huang, Ying" <ying.huang@intel.com>
Reviewed-by: default avatarJonathan Cameron <Jonathan.Cameron@huawie.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Gregory Price <gourry.memverge@gmail.com>
Cc: Hao Xiang <hao.xiang@bytedance.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Ravi Jonnalagadda <ravis.opensrc@micron.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      a72a30af
  3. 26 Apr, 2024 38 commits
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