[PATCH] drm/amdkfd: option to disable system mem limit

[Alex Deucher]

On Tue, Aug 4, 2020 at 1:27 PM Felix Kuehling <felix.kuehling at amd.com> wrote:
>
> Am 2020-07-27 um 9:24 a.m. schrieb Philip Yang:
> > If multiple process share system memory through /dev/shm, KFD allocate
> > memory should not fail if it reachs the system memory limit because
> > one copy of physical system memory are shared by multiple process.
> >
> > Add module parameter to provide user option to disable system memory
> > limit check, to run multiple process share memory application. By
> > default the system memory limit is on.
> >
> > Print out debug message to warn user if KFD allocate memory failed
> > because of system memory limit.
> >
> > Signed-off-by: Philip Yang <Philip.Yang at amd.com>
> > ---
> >  drivers/gpu/drm/amd/amdgpu/amdgpu.h              | 2 ++
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 9 ++++++++-
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c          | 9 +++++++++
> >  3 files changed, 19 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> > index e97c088d03b3..3c0d5ecfe0d5 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> > @@ -187,9 +187,11 @@ extern int amdgpu_force_asic_type;
> >  #ifdef CONFIG_HSA_AMD
> >  extern int sched_policy;
> >  extern bool debug_evictions;
> > +extern bool no_system_mem_limit;
> >  #else
> >  static const int sched_policy = KFD_SCHED_POLICY_HWS;
> >  static const bool debug_evictions; /* = false */
> > +static const bool no_system_mem_limit;
> >  #endif
> >
> >  extern int amdgpu_tmz;
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> > index 8703aa1fe4a5..502e8204c012 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> > @@ -99,7 +99,10 @@ void amdgpu_amdkfd_gpuvm_init_mem_limits(void)
> >       mem *= si.mem_unit;
> >
> >       spin_lock_init(&kfd_mem_limit.mem_limit_lock);
> > -     kfd_mem_limit.max_system_mem_limit = mem - (mem >> 4);
> > +     if (no_system_mem_limit)
> > +             kfd_mem_limit.max_system_mem_limit = U64_MAX;
> > +     else
> > +             kfd_mem_limit.max_system_mem_limit = mem - (mem >> 4);
> >       kfd_mem_limit.max_ttm_mem_limit = (mem >> 1) - (mem >> 3);
> >       pr_debug("Kernel memory limit %lluM, TTM limit %lluM\n",
> >               (kfd_mem_limit.max_system_mem_limit >> 20),
> > @@ -148,6 +151,10 @@ static int amdgpu_amdkfd_reserve_mem_limit(struct amdgpu_device *adev,
> >
> >       spin_lock(&kfd_mem_limit.mem_limit_lock);
> >
> > +     if (kfd_mem_limit.system_mem_used + system_mem_needed >
> > +         kfd_mem_limit.max_system_mem_limit)
> > +             pr_debug("Set no_system_mem_limit if using shared memory\n");
> > +
> >       if ((kfd_mem_limit.system_mem_used + system_mem_needed >
> >            kfd_mem_limit.max_system_mem_limit) ||
> >           (kfd_mem_limit.ttm_mem_used + ttm_mem_needed >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> > index 6291f5f0d223..e9acd0a9f327 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> > @@ -715,6 +715,15 @@ MODULE_PARM_DESC(queue_preemption_timeout_ms, "queue preemption timeout in ms (1
> >  bool debug_evictions;
> >  module_param(debug_evictions, bool, 0644);
> >  MODULE_PARM_DESC(debug_evictions, "enable eviction debug messages (false = default)");
> > +
> > +/**
> > + * DOC: no_system_mem_limit(bool)
> > + * Disable system memory limit, to support multiple process shared memory
> > + */
> > +bool no_system_mem_limit;
> > +module_param(no_system_mem_limit, bool, 0644);
>
> The permissions suggest that this parameter is writable at runtime using
> sysfs. However, the parameter is only read once during module init. So
> any runtime changes to this parameter will not take effect.
>
> You can fix this in two ways:
>
>  1. Make the parameter read only
>  2. Change the implementation of amdgpu_amdkfd_reserve_mem_limit to
>     check the parameter every time and only apply the system memory
>     limit check if necessary
>
> I think the second option is preferable, because it allows user to
> experiment with this without rebooting.

Agreed.  If we go with that approach, maybe just drop the module
parameter altogether and just let the user set it manually per device
at runtime.

Alex

>
> Regards,
>   Felix
>
>
> > +MODULE_PARM_DESC(no_system_mem_limit, "disable system memory limit (false = default)");
> > +
> >  #endif
> >
> >  /**
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