On Tue, Jan 31, 2023 at 3:24 AM Alistair Popple <apopple@xxxxxxxxxx> wrote: > > > Yosry Ahmed <yosryahmed@xxxxxxxxxx> writes: > > > On Mon, Jan 30, 2023 at 5:07 PM Alistair Popple <apopple@xxxxxxxxxx> wrote: > >> > >> > >> Yosry Ahmed <yosryahmed@xxxxxxxxxx> writes: > >> > >> > On Mon, Jan 23, 2023 at 9:43 PM Alistair Popple <apopple@xxxxxxxxxx> wrote: > >> >> > >> >> Having large amounts of unmovable or unreclaimable memory in a system > >> >> can lead to system instability due to increasing the likelihood of > >> >> encountering out-of-memory conditions. Therefore it is desirable to > >> >> limit the amount of memory users can lock or pin. > >> >> > >> >> From userspace such limits can be enforced by setting > >> >> RLIMIT_MEMLOCK. However there is no standard method that drivers and > >> >> other in-kernel users can use to check and enforce this limit. > >> >> > >> >> This has lead to a large number of inconsistencies in how limits are > >> >> enforced. For example some drivers will use mm->locked_mm while others > >> >> will use mm->pinned_mm or user->locked_mm. It is therefore possible to > >> >> have up to three times RLIMIT_MEMLOCKED pinned. > >> >> > >> >> Having pinned memory limited per-task also makes it easy for users to > >> >> exceed the limit. For example drivers that pin memory with > >> >> pin_user_pages() it tends to remain pinned after fork. To deal with > >> >> this and other issues this series introduces a cgroup for tracking and > >> >> limiting the number of pages pinned or locked by tasks in the group. > >> >> > >> >> However the existing behaviour with regards to the rlimit needs to be > >> >> maintained. Therefore the lesser of the two limits is > >> >> enforced. Furthermore having CAP_IPC_LOCK usually bypasses the rlimit, > >> >> but this bypass is not allowed for the cgroup. > >> >> > >> >> The first part of this series converts existing drivers which > >> >> open-code the use of locked_mm/pinned_mm over to a common interface > >> >> which manages the refcounts of the associated task/mm/user > >> >> structs. This ensures accounting of pages is consistent and makes it > >> >> easier to add charging of the cgroup. > >> >> > >> >> The second part of the series adds the cgroup and converts core mm > >> >> code such as mlock over to charging the cgroup before finally > >> >> introducing some selftests. > >> > > >> > > >> > I didn't go through the entire series, so apologies if this was > >> > mentioned somewhere, but do you mind elaborating on why this is added > >> > as a separate cgroup controller rather than an extension of the memory > >> > cgroup controller? > >> > >> One of my early prototypes actually did add this to the memcg > >> controller. However pinned pages fall under their own limit, and we > >> wanted to always account pages to the cgroup of the task using the > >> driver rather than say folio_memcg(). So adding it to memcg didn't seem > >> to have much benefit as we didn't end up using any of the infrastructure > >> provided by memcg. Hence I thought it was clearer to just add it as it's > >> own controller. > > > > To clarify, you account and limit pinned memory based on the cgroup of > > the process pinning the pages, not based on the cgroup that the pages > > are actually charged to? Is my understanding correct? > > That's correct. Interesting. > > > IOW, you limit the amount of memory that processes in a cgroup can > > pin, not the amount of memory charged to a cgroup that can be pinned? > > Right, that's a good clarification which I might steal and add to the > cover letter. Feel free to :) Please also clarify this in the code/docs. Glancing through the patches I was asking myself multiple times why this is not "memory.pinned.[current/max]" or similar. > > >> > >> - Alistair > >> > >> >> > >> >> > >> >> As I don't have access to systems with all the various devices I > >> >> haven't been able to test all driver changes. Any help there would be > >> >> appreciated. > >> >> > >> >> Alistair Popple (19): > >> >> mm: Introduce vm_account > >> >> drivers/vhost: Convert to use vm_account > >> >> drivers/vdpa: Convert vdpa to use the new vm_structure > >> >> infiniband/umem: Convert to use vm_account > >> >> RMDA/siw: Convert to use vm_account > >> >> RDMA/usnic: convert to use vm_account > >> >> vfio/type1: Charge pinned pages to pinned_vm instead of locked_vm > >> >> vfio/spapr_tce: Convert accounting to pinned_vm > >> >> io_uring: convert to use vm_account > >> >> net: skb: Switch to using vm_account > >> >> xdp: convert to use vm_account > >> >> kvm/book3s_64_vio: Convert account_locked_vm() to vm_account_pinned() > >> >> fpga: dfl: afu: convert to use vm_account > >> >> mm: Introduce a cgroup for pinned memory > >> >> mm/util: Extend vm_account to charge pages against the pin cgroup > >> >> mm/util: Refactor account_locked_vm > >> >> mm: Convert mmap and mlock to use account_locked_vm > >> >> mm/mmap: Charge locked memory to pins cgroup > >> >> selftests/vm: Add pins-cgroup selftest for mlock/mmap > >> >> > >> >> MAINTAINERS | 8 +- > >> >> arch/powerpc/kvm/book3s_64_vio.c | 10 +- > >> >> arch/powerpc/mm/book3s64/iommu_api.c | 29 +-- > >> >> drivers/fpga/dfl-afu-dma-region.c | 11 +- > >> >> drivers/fpga/dfl-afu.h | 1 +- > >> >> drivers/infiniband/core/umem.c | 16 +- > >> >> drivers/infiniband/core/umem_odp.c | 6 +- > >> >> drivers/infiniband/hw/usnic/usnic_uiom.c | 13 +- > >> >> drivers/infiniband/hw/usnic/usnic_uiom.h | 1 +- > >> >> drivers/infiniband/sw/siw/siw.h | 2 +- > >> >> drivers/infiniband/sw/siw/siw_mem.c | 20 +-- > >> >> drivers/infiniband/sw/siw/siw_verbs.c | 15 +- > >> >> drivers/vdpa/vdpa_user/vduse_dev.c | 20 +-- > >> >> drivers/vfio/vfio_iommu_spapr_tce.c | 15 +- > >> >> drivers/vfio/vfio_iommu_type1.c | 59 +---- > >> >> drivers/vhost/vdpa.c | 9 +- > >> >> drivers/vhost/vhost.c | 2 +- > >> >> drivers/vhost/vhost.h | 1 +- > >> >> include/linux/cgroup.h | 20 ++- > >> >> include/linux/cgroup_subsys.h | 4 +- > >> >> include/linux/io_uring_types.h | 3 +- > >> >> include/linux/kvm_host.h | 1 +- > >> >> include/linux/mm.h | 5 +- > >> >> include/linux/mm_types.h | 88 ++++++++- > >> >> include/linux/skbuff.h | 6 +- > >> >> include/net/sock.h | 2 +- > >> >> include/net/xdp_sock.h | 2 +- > >> >> include/rdma/ib_umem.h | 1 +- > >> >> io_uring/io_uring.c | 20 +-- > >> >> io_uring/notif.c | 4 +- > >> >> io_uring/notif.h | 10 +- > >> >> io_uring/rsrc.c | 38 +--- > >> >> io_uring/rsrc.h | 9 +- > >> >> mm/Kconfig | 11 +- > >> >> mm/Makefile | 1 +- > >> >> mm/internal.h | 2 +- > >> >> mm/mlock.c | 76 +------ > >> >> mm/mmap.c | 76 +++---- > >> >> mm/mremap.c | 54 +++-- > >> >> mm/pins_cgroup.c | 273 ++++++++++++++++++++++++- > >> >> mm/secretmem.c | 6 +- > >> >> mm/util.c | 196 +++++++++++++++-- > >> >> net/core/skbuff.c | 47 +--- > >> >> net/rds/message.c | 9 +- > >> >> net/xdp/xdp_umem.c | 38 +-- > >> >> tools/testing/selftests/vm/Makefile | 1 +- > >> >> tools/testing/selftests/vm/pins-cgroup.c | 271 ++++++++++++++++++++++++- > >> >> virt/kvm/kvm_main.c | 3 +- > >> >> 48 files changed, 1114 insertions(+), 401 deletions(-) > >> >> create mode 100644 mm/pins_cgroup.c > >> >> create mode 100644 tools/testing/selftests/vm/pins-cgroup.c > >> >> > >> >> base-commit: 2241ab53cbb5cdb08a6b2d4688feb13971058f65 > >> >> -- > >> >> git-series 0.9.1 > >> >> > >> >
