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From: Jason Gunthorpe <jgg@nvidia.com>
To: Alistair Popple <apopple@nvidia.com>
Cc: linux-mm@kvack.org, cgroups@vger.kernel.org,
	linux-kernel@vger.kernel.org, jhubbard@nvidia.com,
	tjmercier@google.com, hannes@cmpxchg.org, surenb@google.com,
	mkoutny@suse.com, daniel@ffwll.ch
Subject: Re: [RFC PATCH 00/19] mm: Introduce a cgroup to limit the amount of locked and pinned memory
Date: Tue, 24 Jan 2023 16:12:00 -0400	[thread overview]
Message-ID: <Y9A7kDjm3ZFAttRR@nvidia.com> (raw)
In-Reply-To: <cover.f52b9eb2792bccb8a9ecd6bc95055705cfe2ae03.1674538665.git-series.apopple@nvidia.com>

On Tue, Jan 24, 2023 at 04:42:29PM +1100, Alistair Popple 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.
>
> 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.

I'm excited by this series, thanks for making it.

The pin accounting has been a long standing problem and cgroups will
really help!

Jason

  parent reply	other threads:[~2023-01-24 20:12 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-24  5:42 [RFC PATCH 00/19] mm: Introduce a cgroup to limit the amount of locked and pinned memory Alistair Popple
2023-01-24  5:42 ` [RFC PATCH 01/19] mm: Introduce vm_account Alistair Popple
2023-01-24  6:29   ` Christoph Hellwig
2023-01-24 14:32   ` Jason Gunthorpe
2023-01-30 11:36     ` Alistair Popple
2023-01-31 14:00   ` David Hildenbrand
2023-01-24  5:42 ` [RFC PATCH 02/19] drivers/vhost: Convert to use vm_account Alistair Popple
2023-01-24  5:55   ` Michael S. Tsirkin
2023-01-30 10:43     ` Alistair Popple
2023-01-24 14:34   ` Jason Gunthorpe
2023-01-24  5:42 ` [RFC PATCH 03/19] drivers/vdpa: Convert vdpa to use the new vm_structure Alistair Popple
2023-01-24 14:35   ` Jason Gunthorpe
2023-01-24  5:42 ` [RFC PATCH 04/19] infiniband/umem: Convert to use vm_account Alistair Popple
2023-01-24  5:42 ` [RFC PATCH 05/19] RMDA/siw: " Alistair Popple
2023-01-24 14:37   ` Jason Gunthorpe
2023-01-24 15:22     ` Bernard Metzler
2023-01-24 15:56     ` Bernard Metzler
2023-01-30 11:34       ` Alistair Popple
2023-01-30 13:27         ` Bernard Metzler
2023-01-24  5:42 ` [RFC PATCH 06/19] RDMA/usnic: convert " Alistair Popple
2023-01-24 14:41   ` Jason Gunthorpe
2023-01-30 11:10     ` Alistair Popple
2023-01-24  5:42 ` [RFC PATCH 07/19] vfio/type1: Charge pinned pages to pinned_vm instead of locked_vm Alistair Popple
2023-01-24  5:42 ` [RFC PATCH 08/19] vfio/spapr_tce: Convert accounting to pinned_vm Alistair Popple
2023-01-24  5:42 ` [RFC PATCH 09/19] io_uring: convert to use vm_account Alistair Popple
2023-01-24 14:44   ` Jason Gunthorpe
2023-01-30 11:12     ` Alistair Popple
2023-01-30 13:21       ` Jason Gunthorpe
2023-01-24  5:42 ` [RFC PATCH 10/19] net: skb: Switch to using vm_account Alistair Popple
2023-01-24 14:51   ` Jason Gunthorpe
2023-01-30 11:17     ` Alistair Popple
2023-02-06  4:36       ` Alistair Popple
2023-02-06 13:14         ` Jason Gunthorpe
2023-01-24  5:42 ` [RFC PATCH 11/19] xdp: convert to use vm_account Alistair Popple
2023-01-24  5:42 ` [RFC PATCH 12/19] kvm/book3s_64_vio: Convert account_locked_vm() to vm_account_pinned() Alistair Popple
2023-01-24  5:42 ` [RFC PATCH 13/19] fpga: dfl: afu: convert to use vm_account Alistair Popple
2023-01-24  5:42 ` [RFC PATCH 14/19] mm: Introduce a cgroup for pinned memory Alistair Popple
2023-01-27 21:44   ` Tejun Heo
2023-01-30 13:20     ` Jason Gunthorpe
2023-01-24  5:42 ` [RFC PATCH 15/19] mm/util: Extend vm_account to charge pages against the pin cgroup Alistair Popple
2023-01-24  5:42 ` [RFC PATCH 16/19] mm/util: Refactor account_locked_vm Alistair Popple
2023-01-24  5:42 ` [RFC PATCH 17/19] mm: Convert mmap and mlock to use account_locked_vm Alistair Popple
2023-01-24  5:42 ` [RFC PATCH 18/19] mm/mmap: Charge locked memory to pins cgroup Alistair Popple
2023-01-24  5:42 ` [RFC PATCH 19/19] selftests/vm: Add pins-cgroup selftest for mlock/mmap Alistair Popple
2023-01-24 18:26 ` [RFC PATCH 00/19] mm: Introduce a cgroup to limit the amount of locked and pinned memory Yosry Ahmed
2023-01-31  0:54   ` Alistair Popple
2023-01-31  5:14     ` Yosry Ahmed
2023-01-31 11:22       ` Alistair Popple
2023-01-31 19:49         ` Yosry Ahmed
2023-01-24 20:12 ` Jason Gunthorpe [this message]
2023-01-31 13:57   ` David Hildenbrand
2023-01-31 14:03     ` Jason Gunthorpe
2023-01-31 14:06       ` David Hildenbrand
2023-01-31 14:10         ` Jason Gunthorpe
2023-01-31 14:15           ` David Hildenbrand
2023-01-31 14:21             ` Jason Gunthorpe

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