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Instead of handling it like a context param, unconditionally set it when
intel_contexts are created. For years we've had the idea of a watchdog
uAPI floating about. The aim was for media, so that they could set very
tight deadlines for their transcodes jobs, so that if you have a corrupt
bitstream (especially for decoding) you don't hang your desktop too
hard. But it's been stuck in limbo since forever, and this simplifies
things a bit in preparation for the proto-context work. If we decide to
actually make said uAPI a reality, we can do it through the proto-
context easily enough.
This does mean that we move from reading the request_timeout_ms param
once per engine when engines are created instead of once at context
creation. If someone changes request_timeout_ms between creating a
context and setting engines, it will mean that they get the new timeout.
If someone races setting request_timeout_ms and context creation, they
can theoretically end up with different timeouts. However, since both
of these are fairly harmless and require changing kernel params, we
don't care.
v2 (Tvrtko Ursulin):
- Add a comment about races with request_timeout_ms
Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210708154835.528166-5-jason@jlekstrand.net
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@jlekstrand.net>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210708154835.528166-2-jason@jlekstrand.net
A new Kconfig option CONFIG_DRM_I915_REQUEST_TIMEOUT is added, defaulting
to 20s, and this timeout is applied to all users contexts using the
previously added watchdog facility.
Result of this is that any user submission will simply fail after this
timeout, either causing a reset (for non-preemptable), or incomplete
results.
This can have an effect that workloads which used to work fine will
suddenly start failing. Even workloads comprised of short batches but in
long dependency chains can be terminated.
And because of lack of agreement on usefulness and safety of fence error
propagation this partial execution can be invisible to userspace even if
it is "listening" to returned fence status.
Another interaction is with hangcheck where care needs to be taken timeout
is not set lower or close to three times the heartbeat interval. Otherwise
a hang in any application can cause complete termination of all
submissions from unrelated clients. Any users modifying the per engine
heartbeat intervals therefore need to be aware of this potential denial of
service to avoid inadvertently enabling it.
Given all this I am personally not convinced the scheme is a good idea.
Intuitively it feels object importers would be better positioned to
enforce the time they are willing to wait for something to complete.
v2:
* Improved commit message and Kconfig text.
* Pull in some helper code from patch which got dropped.
v3:
* Bump timeout to 20s to see if it helps Tigerlake.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210324121335.2307063-7-tvrtko.ursulin@linux.intel.com
