- 29 Jul, 2019 1 commit
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Chris Wilson authored
Remember to keep the rings pinned as well as the context image until the GPU is no longer active. v2: Introduce a ring->pin_count primarily to hide the mock_ring that doesn't fit into the normal GGTT vma picture. v3: Order is important in teardown, ringbuffer submission needs to drop the pin count on the engine->kernel_context before it can gleefully free its ring. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110946 Fixes: ce476c80 ("drm/i915: Keep contexts pinned until after the next kernel context switch") Signed-off-by:
Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Reviewed-by:
Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190619170135.15281-1-chris@chris-wilson.co.uk (cherry picked from commit 09c5ab38 ) Signed-off-by:
Jani Nikula <jani.nikula@intel.com>
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- 19 Jun, 2019 1 commit
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Chris Wilson authored
The idea behind keeping the saturation mask local to a context backfired spectacularly. The premise with the local mask was that we would be more proactive in attempting to use semaphores after each time the context idled, and that all new contexts would attempt to use semaphores ignoring the current state of the system. This turns out to be horribly optimistic. If the system state is still oversaturated and the existing workloads have all stopped using semaphores, the new workloads would attempt to use semaphores and be deprioritised behind real work. The new contexts would not switch off using semaphores until their initial batch of low priority work had completed. Given sufficient backload load of equal user priority, this would completely starve the new work of any GPU time. To compensate, remove the local tracking in favour of keeping it as global state on the engine -- once the system is saturated and semaphores are disabled, everyone stops attempting to use semaphores until the system is idle again. One of the reason for preferring local context tracking was that it worked with virtual engines, so for switching to global state we could either do a complete check of all the virtual siblings or simply disable semaphores for those requests. This takes the simpler approach of disabling semaphores on virtual engines. The downside is that the decision that the engine is saturated is a local measure -- we are only checking whether or not this context was scheduled in a timely fashion, it may be legitimately delayed due to user priorities. We still have the same dilemma though, that we do not want to employ the semaphore poll unless it will be used. v2: Explain why we need to assume the worst wrt virtual engines. Fixes: ca6e56f6 ("drm/i915: Disable semaphore busywaits on saturated systems") Signed-off-by:
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- 14 Jun, 2019 2 commits
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Chris Wilson authored
We need to keep the context image pinned in memory until after the GPU has finished writing into it. Since it continues to write as we signal the final breadcrumb, we need to keep it pinned until the request after it is complete. Currently we know the order in which requests execute on each engine, and so to remove that presumption we need to identify a request/context-switch we know must occur after our completion. Any request queued after the signal must imply a context switch, for simplicity we use a fresh request from the kernel context. The sequence of operations for keeping the context pinned until saved is: - On context activation, we preallocate a node for each physical engine the context may operate on. This is to avoid allocations during unpinning, which may be from inside FS_RECLAIM context (aka the shrinker) - On context deactivation on retirement of the last active request (which is before we know the context has been saved), we add the preallocated node onto a barrier list on each engine - On engine idling, we emit a switch to kernel context. When this switch completes, we know that all previous contexts must have been saved, and so on retiring this request we can finally unpin all the contexts that were marked as deactivated prior to the switch. We can enhance this in future by flushing all the idle contexts on a regular heartbeat pulse of a switch to kernel context, which will also be used to check for hung engines. v2: intel_context_active_acquire/_release Signed-off-by:
Mika Kuoppala <mika.kuoppala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190614164606.15633-1-chris@chris-wilson.co.uk
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Daniele Ceraolo Spurio authored
Matching the underlying get/put functions. Signed-off-by:
Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com> Cc: Imre Deak <imre.deak@intel.com> Reviewed-by:
Imre Deak <imre.deak@intel.com> Signed-off-by:
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- 28 May, 2019 1 commit
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Chris Wilson authored
Continuing the theme of separating out the GEM clutter. Signed-off-by:
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- 04 May, 2019 1 commit
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Chris Wilson authored
Asking the GPU to busywait on a memory address, perhaps not unexpectedly in hindsight for a shared system, leads to bus contention that affects CPU programs trying to concurrently access memory. This can manifest as a drop in transcode throughput on highly over-saturated workloads. The only clue offered by perf, is that the bus-cycles (perf stat -e bus-cycles) jumped by 50% when enabling semaphores. This corresponds with extra CPU active cycles being attributed to intel_idle's mwait. This patch introduces a heuristic to try and detect when more than one client is submitting to the GPU pushing it into an oversaturated state. As we already keep track of when the semaphores are signaled, we can inspect their state on submitting the busywait batch and if we planned to use a semaphore but were too late, conclude that the GPU is overloaded and not try to use semaphores in future requests. In practice, this means we optimistically try to use semaphores for the first frame of a transcode job split over multiple engines, and fail if there are multiple clients active and continue not to use semaphores for the subsequent frames in the sequence. Periodically, we try to optimistically switch semaphores back on whenever the client waits to catch up with the transcode results. With 1 client, on Broxton J3455, with the relative fps normalized by %cpu: x no semaphores + drm-tip * patched +------------------------------------------------------------------------+ | * | | *+ | | **+ | | **+ x | | x * +**+ x | | x x * * +***x xx | | x x * * *+***x *x | | x x* + * * *****x *x x | | + x xx+x* + *** * ********* x * | | + x xx+x* * *** +** ********* xx * | | * + ++++* + x*x****+*+* ***+*************+x* * | |*+ +** *+ + +* + *++****** *xxx**********x***+*****************+*++ *| | |__________A_____M_____| | | |_______________A____M_________| | | |____________A___M________| | +------------------------------------------------------------------------+ N Min Max Median Avg Stddev x 120 2.60475 3.50941 3.31123 3.2143953 0.21117399 + 120 2.3826 3.57077 3.25101 3.1414161 0.28146407 Difference at 95.0% confidence -0.0729792 +/- 0.0629585 -2.27039% +/- 1.95864% (Student's t, pooled s = 0.248814) * 120 2.35536 3.66713 3.2849 3.2059917 0.24618565 No difference proven at 95.0% confidence With 10 clients over-saturating the pipeline: x no semaphores + drm-tip * patched +------------------------------------------------------------------------+ | ++ ** | | ++ ** | | ++ ** | | ++ ** | | ++ xx *** | | ++ xx *** | | ++ xxx*** | | ++ xxx*** | | +++ xxx*** | | +++ xx**** | | +++ xx**** | | +++ xx**** | | +++ xx**** | | ++++ xx**** | | +++++ xx**** | | +++++ x x****** | | ++++++ xxx******* | | ++++++ xxx******* | | ++++++ xxx******* | | ++++++ xx******** | | ++++++ xxxx******** | | ++++++ xxxx******** | | ++++++++ xxxxx********* | |+ + + + ++++++++ xxx*xx**********x* *| | |__A__| | | |__AM__| | | |__A_| | +------------------------------------------------------------------------+ N Min Max Median Avg Stddev x 120 2.47855 2.8972 2.72376 2.7193402 0.074604933 + 120 1.17367 1.77459 1.71977 1.6966782 0.085850697 Difference at 95.0% confidence -1.02266 +/- 0.0203502 -37.607% +/- 0.748352% (Student's t, pooled s = 0.0804246) * 120 2.57868 3.00821 2.80142 2.7923878 0.058646477 Difference at 95.0% confidence 0.0730476 +/- 0.0169791 2.68622% +/- 0.624383% (Student's t, pooled s = 0.0671018) Indicating that we've recovered the regression from enabling semaphores on this saturated setup, with a hint towards an overall improvement. Very similar, but of smaller magnitude, results are observed on both Skylake(gt2) and Kabylake(gt4). This may be due to the reduced impact of bus-cycles, where we see a 50% hit on Broxton, it is only 10% on the big core, in this particular test. One observation to make here is that for a greedy client trying to maximise its own throughput, using semaphores is the right choice. It is only the holistic system-wide view that semaphores of one client impacts another and reduces the overall throughput where we would choose to disable semaphores. The most noticeable negactive impact this has is on the no-op microbenchmarks, which are also very notable for having no cpu bus load. In particular, this increases the runtime and energy consumption of gem_exec_whisper. Signed-off-by:
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- 26 Apr, 2019 4 commits
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Chris Wilson authored
We no longer need to track the active intel_contexts within each engine, allowing us to drop a tricky mutex_lock from inside unpin (which may occur inside fs_reclaim). Signed-off-by:
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Chris Wilson authored
We switched to a tree of per-engine HW context to accommodate the introduction of virtual engines. However, we plan to also support multiple instances of the same engine within the GEM context, defeating our use of the engine as a key to looking up the HW context. Just allocate a logical per-engine instance and always use an index into the ctx->engines[]. Later on, this ctx->engines[] may be replaced by a user specified map. v2: Add for_each_gem_engine() helper to iterator within the engines lock v3: intel_context_create_request() helper v4: s/unsigned long/unsigned int/ 4 billion engines is quite enough. v5: Push iterator locking to caller Signed-off-by:
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Chris Wilson authored
Move the intel_context_instance() to the caller so that we can decouple ourselves from one context instance per engine. v2: Rename pin_lock() to lock_pinned(), hopefully that is clearer. Signed-off-by:
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Chris Wilson authored
We want to pass in a intel_context into intel_context_pin() and that requires us to first be able to lookup the intel_context! Signed-off-by:
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- 24 Apr, 2019 4 commits
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Chris Wilson authored
In the current scheme, on submitting a request we take a single global GEM wakeref, which trickles down to wake up all GT power domains. This is undesirable as we would like to be able to localise our power management to the available power domains and to remove the global GEM operations from the heart of the driver. (The intent there is to push global GEM decisions to the boundary as used by the GEM user interface.) Now during request construction, each request is responsible via its logical context to acquire a wakeref on each power domain it intends to utilize. Currently, each request takes a wakeref on the engine(s) and the engines themselves take a chipset wakeref. This gives us a transition on each engine which we can extend if we want to insert more powermangement control (such as soft rc6). The global GEM operations that currently require a struct_mutex are reduced to listening to pm events from the chipset GT wakeref. As we reduce the struct_mutex requirement, these listeners should evaporate. Perhaps the biggest immediate change is that this removes the struct_mutex requirement around GT power management, allowing us greater flexibility in request construction. Another important knock-on effect, is that by tracking engine usage, we can insert a switch back to the kernel context on that engine immediately, avoiding any extra delay or inserting global synchronisation barriers. This makes tracking when an engine and its associated contexts are idle much easier -- important for when we forgo our assumed execution ordering and need idle barriers to unpin used contexts. In the process, it means we remove a large chunk of code whose only purpose was to switch back to the kernel context. Signed-off-by:
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Chris Wilson authored
We wish to start segregating the power management into different control domains, both with respect to the hardware and the user interface. The first step is that at the lowest level flow of requests, we want to process a context event (and not a global GEM operation). In this patch, we introduce the context callbacks that in future patches will be redirected to per-engine interfaces leading to global operations as required. The intent is that this will be guarded by the timeline->mutex, except that retiring has not quite finished transitioning over from being guarded by struct_mutex. So at the moment it is protected by struct_mutex with a reminded to switch. v2: Rename default handlers to intel_context_enter_engine. Signed-off-by:
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Chris Wilson authored
Start partitioning off the code that talks to the hardware (GT) from the uapi layers and move the device facing code under gt/ One casualty is s/intel_ringbuffer.h/intel_engine.h/ with the plan to subdivide that header and body further (and split out the submission code from the ringbuffer and logical context handling). This patch aims to be simple motion so git can fixup inflight patches with little mess. Signed-off-by:
Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Acked-by:
Rodrigo Vivi <rodrigo.vivi@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190424174839.7141-1-chris@chris-wilson.co.uk
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Chris Wilson authored
As we push for better compartmentalisation, it is more convenient to copy the default sseu configuration from the engine into the derived logical context, than it is to dig it out from i915->runtime_info. v2: Use intel_sseu_from_device_info() to describe the converter Signed-off-by:
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- 19 Mar, 2019 2 commits
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Chris Wilson authored
For virtual engines, we need to keep the HW context alive while it remains in use. For regular HW contexts, they are created and kept alive until the end of the GEM context. For simplicity, generalise the requirements and keep an active reference to each HW context. Signed-off-by:
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Chris Wilson authored
On unpinning the intel_context, we remove it from the active list inside the GEM context. This list is supposed to be guarded by the GEM context mutex, so remember to take it! Fixes: 7e3d9a59 ("drm/i915: Track active engines within a context") Signed-off-by:
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- 08 Mar, 2019 3 commits
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Chris Wilson authored
Introduce a mutex to start locking the HW contexts independently of struct_mutex, with a view to reducing the coarse struct_mutex. The intel_context.pin_mutex is used to guard the transition to and from being pinned on the gpu, and so is required before starting to build any request. The intel_context will then remain pinned until the request completes, but the mutex can be released immediately unpin completion of pinning the context. A slight variant of the above is used by per-context sseu that wants to inspect the pinned status of the context, and requires that it remains stable (either !pinned or pinned) across its operation. By using the pin_mutex to serialise operations while pin_count==0, we can take that pin_mutex for stabilise the boolean pin status. v2: for Tvrtko! * Improved commit message. * Dropped _gpu suffix from gen8_modify_rpcs_gpu. v3: Repair the locking for sseu selftests Signed-off-by:
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Chris Wilson authored
Push the intel_context pin callback down from intel_engine_cs onto the context itself by virtue of having a central caller for intel_context_pin() being able to lookup the intel_context itself. Signed-off-by:
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Chris Wilson authored
In preparation for an ever growing number of engines and so ever increasing static array of HW contexts within the GEM context, move the array over to an rbtree, allocated upon first use. Unfortunately, this imposes an rbtree lookup at a few frequent callsites, but we should be able to mitigate those by moving over to using the HW context as our primary type and so only incur the lookup on the boundary with the user GEM context and engines. v2: Check for no HW context in guc_stage_desc_init Signed-off-by:
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