From: Asier Gutierrez <gutierrez.asier@xxxxxxxxxxxxxxxxxxx> Currently THP modes are set globally. It can be an overkill if only some specific app/set of apps need to get benefits from THP usage. Moreover, various apps might need different THP settings. Here we propose a cgroup-based THP control mechanism. THP interface is added to memory cgroup subsystem. Existing global THP control semantics is supported for backward compatibility. When THP modes are set globally all the changes are propagated to memory cgroups. However, when a particular cgroup changes its THP policy, the global THP policy in sysfs remains the same. New memcg files are exposed: memory.thp_enabled and memory.thp_defrag, which have completely the same format as global THP enabled/defrag. Child cgroups inherit THP settings from parent cgroup upon creation. Particular cgroup mode changes aren't propagated to child cgroups. During the memory cgroup attachment stage, the correct slots are added or removed to khugepaged according to the THP policy. Usage examples: Set globally "madvise" mode: # echo madvise > /sys/kernel/mm/transparent_hugepage/enabled # cat /sys/kernel/mm/transparent_hugepage/enabled always [madvise] never All the settings are propagated # cat /sys/fs/cgroup/memory.thp_enabled always [madvise] never # cat /sys/fs/cgroup/test/memory.thp_enabled always [madvise] never Set "always" for some specific cgroup: # echo always > /sys/fs/cgroup/test/memory.thp_enabled # cat /sys/fs/cgroup/test/memory.thp_enabled [always] madvise never Root cgroup remains with "madvise" mode: # cat /sys/fs/cgroup/memory.thp_enabled always [madvise] never When attempting to read global settings we get "mixed state" warning as the THP-mode isn't the same for every cgroup: # cat /sys/kernel/mm/transparent_hugepage/enabled Mixed state: see particular memcg flags! Again, set THP mode globally, make sure everything works fine: # echo never > /sys/kernel/mm/transparent_hugepage/enabled # cat /sys/kernel/mm/transparent_hugepage/enabled always madvise [never] # cat /sys/fs/cgroup/memory.thp_enabled always madvise [never] # cat /sys/fs/cgroup/test/memory.thp_enabled always madvise [never] Here is a simple demo with a test which is doing anon. mmap() and a series of random reads. System is rebooted between the cases. Case 1: Global THP - always. No cgroup. // Global THP stats: AnonHugePages: 391168 kB FileHugePages: 120832 kB FilePmdMapped: 67584 kB // THP stats from *smaps* of the testing process AnonHugePages: 12288 kB Case 2: Global THP - never. Cgroup - always. // Global THP stats: AnonHugePages: 12288 kB FileHugePages: 2048 kB FilePmdMapped: 2048 kB // THP stats from *smaps* of the testing process AnonHugePages: 12288 kB // The cgroup THP stats anon_thp 12582912 file_thp 2097152 Obviously there's a huge difference between the two in terms of global THP usage, thus showing the cgroup approach is beneficial for such cases, when a specific app/set of apps needs THP, but not willing to change anything in the app. code. TODO list: 1. Anonymous mTHP 2. Fine-grained mode selection for different VMA types: "anon|exec|ro|file", to be able to support combinations as: "always + exec", "always + anon", etc. 3. Per-cgroup limit for the THP usage Signed-off-by: Asier Gutierrez <gutierrez.asier@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Anatoly Stepanov <stepanov.anatoly@xxxxxxxxxx> Reviewed-by: Alexander Kozhevnikov <alexander.kozhevnikov@xxxxxxxxxxxxxxxxxxx> Asier Gutierrez, Anatoly Stepanov (3): mm: Add thp_flags control for cgroup mm: Support for huge pages in cgroups mm: Add thp_defrag control for cgroup include/linux/huge_mm.h | 23 +++- include/linux/khugepaged.h | 2 +- include/linux/memcontrol.h | 28 ++++ mm/huge_memory.c | 207 ++++++++++++++++++----------- mm/khugepaged.c | 8 +- mm/memcontrol.c | 262 +++++++++++++++++++++++++++++++++++++ 6 files changed, 449 insertions(+), 81 deletions(-) -- 2.34.1
