On 05/09/2018 11:33, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2018-09-05 10:49:02)
On 04/09/2018 16:31, Chris Wilson wrote:
Future gen reduce the number of bits we will have available to
differentiate between contexts, so reduce the lifetime of the ID
assignment from that of the context to its current active cycle (i.e.
only while it is pinned for use by the HW, will it have a constant ID).
This means that instead of a max of 2k allocated contexts (worst case
before fun with bit twiddling), we instead have a limit of 2k in flight
contexts (minus a few that have been pinned by the kernel or by perf).
To reduce the number of contexts id we require, we allocate a context id
on first and mark it as pinned for as long as the GEM context itself is,
that is we keep it pinned it while active on each engine. If we exhaust
our context id space, then we try to reclaim an id from an idle context.
In the extreme case where all context ids are pinned by active contexts,
we force the system to idle in order to recover ids.
We cannot reduce the scope of an HW-ID to an engine (allowing the same
gem_context to have different ids on each engine) as in the future we
will need to preassign an id before we know which engine the
context is being executed on.
v2: Improved commentary (Tvrtko) [I tried at least]
References: https://bugs.freedesktop.org/show_bug.cgi?id=107788
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
Cc: Michel Thierry <michel.thierry@xxxxxxxxx>
Cc: Michal Wajdeczko <michal.wajdeczko@xxxxxxxxx>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_debugfs.c | 5 +-
drivers/gpu/drm/i915/i915_drv.h | 2 +
drivers/gpu/drm/i915/i915_gem_context.c | 222 +++++++++++++-----
drivers/gpu/drm/i915/i915_gem_context.h | 23 ++
drivers/gpu/drm/i915/intel_lrc.c | 8 +
drivers/gpu/drm/i915/selftests/mock_context.c | 11 +-
6 files changed, 201 insertions(+), 70 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 4ad0e2ed8610..1f7051e97afb 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1953,7 +1953,10 @@ static int i915_context_status(struct seq_file *m, void *unused)
return ret;
list_for_each_entry(ctx, &dev_priv->contexts.list, link) {
- seq_printf(m, "HW context %u ", ctx->hw_id);
+ seq_puts(m, "HW context ");
+ if (!list_empty(&ctx->hw_id_link))
+ seq_printf(m, "%x [pin %u]", ctx->hw_id,
+ atomic_read(&ctx->hw_id_pin_count));
Do you want to put some marker for the unallocated case here?
I was content with absence of marker as indicating it has never had an
id, or it had been revoked.
Who reads this file anyway? There's not one igt where I've thought this
would be useful debug info. Maybe I'm wrong...
True, the file as it is looks weak. It was only a question/suggestion
anyway. Perhaps we can later improve the file to list them in a more
modern/meaningful way.
Regards,
Tvrtko
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