On Tue, Apr 27, 2021 at 4:32 AM Daniel Vetter <daniel@xxxxxxxx> wrote:
>
> On Fri, Apr 23, 2021 at 05:31:11PM -0500, Jason Ekstrand wrote:
> > This reverts commit 88be76cdafc7 ("drm/i915: Allow userspace to specify
> > ringsize on construction"). This API was originally added for OpenCL
> > but the compute-runtime PR has sat open for a year without action so we
> > can still pull it out if we want. I argue we should drop it for three
> > reasons:
> >
> > 1. If the compute-runtime PR has sat open for a year, this clearly
> > isn't that important.
> >
> > 2. It's a very leaky API. Ring size is an implementation detail of the
> > current execlist scheduler and really only makes sense there. It
> > can't apply to the older ring-buffer scheduler on pre-execlist
> > hardware because that's shared across all contexts and it won't
> > apply to the GuC scheduler that's in the pipeline.
> >
> > 3. Having userspace set a ring size in bytes is a bad solution to the
> > problem of having too small a ring. There is no way that userspace
> > has the information to know how to properly set the ring size so
> > it's just going to detect the feature and always set it to the
> > maximum of 512K. This is what the compute-runtime PR does. The
> > scheduler in i915, on the other hand, does have the information to
> > make an informed choice. It could detect if the ring size is a
> > problem and grow it itself. Or, if that's too hard, we could just
> > increase the default size from 16K to 32K or even 64K instead of
> > relying on userspace to do it.
> >
> > Let's drop this API for now and, if someone decides they really care
> > about solving this problem, they can do it properly.
> >
> > Signed-off-by: Jason Ekstrand <jason@xxxxxxxxxxxxxx>
>
> Two things:
> - I'm assuming you have an igt change to make sure we get EINVAL for both
> set and getparam now? Just to make sure.
I've written up some quick tests. I'll send them out in the next
version of the IGT series or as a separate series if that one gets
reviewed without comment (unlikely).
> - intel_context->ring is either a ring pointer when CONTEXT_ALLOC_BIT is
> set in ce->flags, or the size of the ring stored in the pointer if not.
> I'm seriously hoping you get rid of this complexity with your
> proto-context series, and also delete __intel_context_ring_size() in the
> end. That function has no business existing imo.
I hadn't done that yet, no. But I typed up a patch today which I'll
send out with the next version of this series which does this.
--Jason
> If not, please make sure that's the case.
>
> Aside from these patch looks good.
>
> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
>
> > ---
> > drivers/gpu/drm/i915/Makefile | 1 -
> > drivers/gpu/drm/i915/gem/i915_gem_context.c | 85 +------------------
> > drivers/gpu/drm/i915/gt/intel_context_param.c | 63 --------------
> > drivers/gpu/drm/i915/gt/intel_context_param.h | 3 -
> > include/uapi/drm/i915_drm.h | 20 +----
> > 5 files changed, 4 insertions(+), 168 deletions(-)
> > delete mode 100644 drivers/gpu/drm/i915/gt/intel_context_param.c
> >
> > diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> > index d0d936d9137bc..afa22338fa343 100644
> > --- a/drivers/gpu/drm/i915/Makefile
> > +++ b/drivers/gpu/drm/i915/Makefile
> > @@ -88,7 +88,6 @@ gt-y += \
> > gt/gen8_ppgtt.o \
> > gt/intel_breadcrumbs.o \
> > gt/intel_context.o \
> > - gt/intel_context_param.o \
> > gt/intel_context_sseu.o \
> > gt/intel_engine_cs.o \
> > gt/intel_engine_heartbeat.o \
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > index fd8ee52e17a47..e52b85b8f923d 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > @@ -1335,63 +1335,6 @@ static int set_ppgtt(struct drm_i915_file_private *file_priv,
> > return err;
> > }
> >
> > -static int __apply_ringsize(struct intel_context *ce, void *sz)
> > -{
> > - return intel_context_set_ring_size(ce, (unsigned long)sz);
> > -}
> > -
> > -static int set_ringsize(struct i915_gem_context *ctx,
> > - struct drm_i915_gem_context_param *args)
> > -{
> > - if (!HAS_LOGICAL_RING_CONTEXTS(ctx->i915))
> > - return -ENODEV;
> > -
> > - if (args->size)
> > - return -EINVAL;
> > -
> > - if (!IS_ALIGNED(args->value, I915_GTT_PAGE_SIZE))
> > - return -EINVAL;
> > -
> > - if (args->value < I915_GTT_PAGE_SIZE)
> > - return -EINVAL;
> > -
> > - if (args->value > 128 * I915_GTT_PAGE_SIZE)
> > - return -EINVAL;
> > -
> > - return context_apply_all(ctx,
> > - __apply_ringsize,
> > - __intel_context_ring_size(args->value));
> > -}
> > -
> > -static int __get_ringsize(struct intel_context *ce, void *arg)
> > -{
> > - long sz;
> > -
> > - sz = intel_context_get_ring_size(ce);
> > - GEM_BUG_ON(sz > INT_MAX);
> > -
> > - return sz; /* stop on first engine */
> > -}
> > -
> > -static int get_ringsize(struct i915_gem_context *ctx,
> > - struct drm_i915_gem_context_param *args)
> > -{
> > - int sz;
> > -
> > - if (!HAS_LOGICAL_RING_CONTEXTS(ctx->i915))
> > - return -ENODEV;
> > -
> > - if (args->size)
> > - return -EINVAL;
> > -
> > - sz = context_apply_all(ctx, __get_ringsize, NULL);
> > - if (sz < 0)
> > - return sz;
> > -
> > - args->value = sz;
> > - return 0;
> > -}
> > -
> > int
> > i915_gem_user_to_context_sseu(struct intel_gt *gt,
> > const struct drm_i915_gem_context_param_sseu *user,
> > @@ -2037,11 +1980,8 @@ static int ctx_setparam(struct drm_i915_file_private *fpriv,
> > ret = set_persistence(ctx, args);
> > break;
> >
> > - case I915_CONTEXT_PARAM_RINGSIZE:
> > - ret = set_ringsize(ctx, args);
> > - break;
> > -
> > case I915_CONTEXT_PARAM_BAN_PERIOD:
> > + case I915_CONTEXT_PARAM_RINGSIZE:
> > default:
> > ret = -EINVAL;
> > break;
> > @@ -2069,18 +2009,6 @@ static int create_setparam(struct i915_user_extension __user *ext, void *data)
> > return ctx_setparam(arg->fpriv, arg->ctx, &local.param);
> > }
> >
> > -static int copy_ring_size(struct intel_context *dst,
> > - struct intel_context *src)
> > -{
> > - long sz;
> > -
> > - sz = intel_context_get_ring_size(src);
> > - if (sz < 0)
> > - return sz;
> > -
> > - return intel_context_set_ring_size(dst, sz);
> > -}
> > -
> > static int clone_engines(struct i915_gem_context *dst,
> > struct i915_gem_context *src)
> > {
> > @@ -2125,12 +2053,6 @@ static int clone_engines(struct i915_gem_context *dst,
> > }
> >
> > intel_context_set_gem(clone->engines[n], dst);
> > -
> > - /* Copy across the preferred ringsize */
> > - if (copy_ring_size(clone->engines[n], e->engines[n])) {
> > - __free_engines(clone, n + 1);
> > - goto err_unlock;
> > - }
> > }
> > clone->num_engines = n;
> > i915_sw_fence_complete(&e->fence);
> > @@ -2490,11 +2412,8 @@ int i915_gem_context_getparam_ioctl(struct drm_device *dev, void *data,
> > args->value = i915_gem_context_is_persistent(ctx);
> > break;
> >
> > - case I915_CONTEXT_PARAM_RINGSIZE:
> > - ret = get_ringsize(ctx, args);
> > - break;
> > -
> > case I915_CONTEXT_PARAM_BAN_PERIOD:
> > + case I915_CONTEXT_PARAM_RINGSIZE:
> > default:
> > ret = -EINVAL;
> > break;
> > diff --git a/drivers/gpu/drm/i915/gt/intel_context_param.c b/drivers/gpu/drm/i915/gt/intel_context_param.c
> > deleted file mode 100644
> > index 65dcd090245d6..0000000000000
> > --- a/drivers/gpu/drm/i915/gt/intel_context_param.c
> > +++ /dev/null
> > @@ -1,63 +0,0 @@
> > -// SPDX-License-Identifier: MIT
> > -/*
> > - * Copyright © 2019 Intel Corporation
> > - */
> > -
> > -#include "i915_active.h"
> > -#include "intel_context.h"
> > -#include "intel_context_param.h"
> > -#include "intel_ring.h"
> > -
> > -int intel_context_set_ring_size(struct intel_context *ce, long sz)
> > -{
> > - int err;
> > -
> > - if (intel_context_lock_pinned(ce))
> > - return -EINTR;
> > -
> > - err = i915_active_wait(&ce->active);
> > - if (err < 0)
> > - goto unlock;
> > -
> > - if (intel_context_is_pinned(ce)) {
> > - err = -EBUSY; /* In active use, come back later! */
> > - goto unlock;
> > - }
> > -
> > - if (test_bit(CONTEXT_ALLOC_BIT, &ce->flags)) {
> > - struct intel_ring *ring;
> > -
> > - /* Replace the existing ringbuffer */
> > - ring = intel_engine_create_ring(ce->engine, sz);
> > - if (IS_ERR(ring)) {
> > - err = PTR_ERR(ring);
> > - goto unlock;
> > - }
> > -
> > - intel_ring_put(ce->ring);
> > - ce->ring = ring;
> > -
> > - /* Context image will be updated on next pin */
> > - } else {
> > - ce->ring = __intel_context_ring_size(sz);
> > - }
> > -
> > -unlock:
> > - intel_context_unlock_pinned(ce);
> > - return err;
> > -}
> > -
> > -long intel_context_get_ring_size(struct intel_context *ce)
> > -{
> > - long sz = (unsigned long)READ_ONCE(ce->ring);
> > -
> > - if (test_bit(CONTEXT_ALLOC_BIT, &ce->flags)) {
> > - if (intel_context_lock_pinned(ce))
> > - return -EINTR;
> > -
> > - sz = ce->ring->size;
> > - intel_context_unlock_pinned(ce);
> > - }
> > -
> > - return sz;
> > -}
> > diff --git a/drivers/gpu/drm/i915/gt/intel_context_param.h b/drivers/gpu/drm/i915/gt/intel_context_param.h
> > index 3ecacc675f414..dffedd983693d 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_context_param.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_context_param.h
> > @@ -10,9 +10,6 @@
> >
> > #include "intel_context.h"
> >
> > -int intel_context_set_ring_size(struct intel_context *ce, long sz);
> > -long intel_context_get_ring_size(struct intel_context *ce);
> > -
> > static inline int
> > intel_context_set_watchdog_us(struct intel_context *ce, u64 timeout_us)
> > {
> > diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> > index 6a34243a7646a..6eefbc6dec01f 100644
> > --- a/include/uapi/drm/i915_drm.h
> > +++ b/include/uapi/drm/i915_drm.h
> > @@ -1721,24 +1721,8 @@ struct drm_i915_gem_context_param {
> > */
> > #define I915_CONTEXT_PARAM_PERSISTENCE 0xb
> >
> > -/*
> > - * I915_CONTEXT_PARAM_RINGSIZE:
> > - *
> > - * Sets the size of the CS ringbuffer to use for logical ring contexts. This
> > - * applies a limit of how many batches can be queued to HW before the caller
> > - * is blocked due to lack of space for more commands.
> > - *
> > - * Only reliably possible to be set prior to first use, i.e. during
> > - * construction. At any later point, the current execution must be flushed as
> > - * the ring can only be changed while the context is idle. Note, the ringsize
> > - * can be specified as a constructor property, see
> > - * I915_CONTEXT_CREATE_EXT_SETPARAM, but can also be set later if required.
> > - *
> > - * Only applies to the current set of engine and lost when those engines
> > - * are replaced by a new mapping (see I915_CONTEXT_PARAM_ENGINES).
> > - *
> > - * Must be between 4 - 512 KiB, in intervals of page size [4 KiB].
> > - * Default is 16 KiB.
> > +/* This API has been removed. On the off chance someone somewhere has
> > + * attempted to use it, never re-use this context param number.
> > */
> > #define I915_CONTEXT_PARAM_RINGSIZE 0xc
> > /* Must be kept compact -- no holes and well documented */
> > --
> > 2.31.1
> >
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
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