Hi Geert,
On Tue, Jan 14, 2025 at 11:16:43AM +0100, Geert Uytterhoeven wrote:
> Hi Maarten,
>
> On Wed, Dec 4, 2024 at 3:32 PM Maarten Lankhorst <dev@xxxxxxxxxxxx> wrote:
> > This code is based on the RDMA and misc cgroup initially, but now
> > uses page_counter. It uses the same min/low/max semantics as the memory
> > cgroup as a result.
> >
> > There's a small mismatch as TTM uses u64, and page_counter long pages.
> > In practice it's not a problem. 32-bits systems don't really come with
> > >=4GB cards and as long as we're consistently wrong with units, it's
> > fine. The device page size may not be in the same units as kernel page
> > size, and each region might also have a different page size (VRAM vs GART
> > for example).
> >
> > The interface is simple:
> > - Call dmem_cgroup_register_region()
> > - Use dmem_cgroup_try_charge to check if you can allocate a chunk of memory,
> > use dmem_cgroup__uncharge when freeing it. This may return an error code,
> > or -EAGAIN when the cgroup limit is reached. In that case a reference
> > to the limiting pool is returned.
> > - The limiting cs can be used as compare function for
> > dmem_cgroup_state_evict_valuable.
> > - After having evicted enough, drop reference to limiting cs with
> > dmem_cgroup_pool_state_put.
> >
> > This API allows you to limit device resources with cgroups.
> > You can see the supported cards in /sys/fs/cgroup/dmem.capacity
> > You need to echo +dmem to cgroup.subtree_control, and then you can
> > partition device memory.
> >
> > Co-developed-by: Friedrich Vock <friedrich.vock@xxxxxx>
> > Signed-off-by: Friedrich Vock <friedrich.vock@xxxxxx>
> > Co-developed-by: Maxime Ripard <mripard@xxxxxxxxxx>
> > Signed-off-by: Maxime Ripard <mripard@xxxxxxxxxx>
> > Signed-off-by: Maarten Lankhorst <dev@xxxxxxxxxxxx>
>
> Thanks for your patch, which is now commit b168ed458ddecc17
> ("kernel/cgroup: Add "dmem" memory accounting cgroup") in drm/drm-next.
>
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -1128,6 +1128,7 @@ config CGROUP_PIDS
> >
> > config CGROUP_RDMA
> > bool "RDMA controller"
> > + select PAGE_COUNTER
>
> This change looks unrelated?
>
> Oh, reading your response to the build error, this should have been below?
Indeed, good catch.
> > help
> > Provides enforcement of RDMA resources defined by IB stack.
> > It is fairly easy for consumers to exhaust RDMA resources, which
> > @@ -1136,6 +1137,15 @@ config CGROUP_RDMA
> > Attaching processes with active RDMA resources to the cgroup
> > hierarchy is allowed even if can cross the hierarchy's limit.
> >
> > +config CGROUP_DMEM
> > + bool "Device memory controller (DMEM)"
> > + help
> > + The DMEM controller allows compatible devices to restrict device
> > + memory usage based on the cgroup hierarchy.
> > +
> > + As an example, it allows you to restrict VRAM usage for applications
> > + in the DRM subsystem.
> > +
>
> Do you envision other users than DRM?
> Perhaps this should depend on DRM for now?
dma-buf heaps and v4l2 support are in progress right now.
Maxime
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