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From: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org
Cc: thomas.hellstrom@intel.com
Subject: Re: [Intel-gfx] [PATCH 16/21] drm/i915/gt: Track signaled breadcrumbs outside of the breadcrumb spinlock
Date: Fri, 31 Jul 2020 16:32:04 +0100	[thread overview]
Message-ID: <ea6ace16-bea5-f71d-8fcf-a96fa61f7cef@linux.intel.com> (raw)
In-Reply-To: <159620835263.21624.6486195506614954052@build.alporthouse.com>


On 31/07/2020 16:12, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2020-07-31 16:06:55)
>>
>> On 30/07/2020 10:37, Chris Wilson wrote:
>>> @@ -191,17 +188,19 @@ static void signal_irq_work(struct irq_work *work)
>>>    {
>>>        struct intel_breadcrumbs *b = container_of(work, typeof(*b), irq_work);
>>>        const ktime_t timestamp = ktime_get();
>>> +     struct llist_node *signal, *sn;
>>>        struct intel_context *ce, *cn;
>>>        struct list_head *pos, *next;
>>> -     LIST_HEAD(signal);
>>> +
>>> +     signal = NULL;
>>> +     if (unlikely(!llist_empty(&b->signaled_requests)))
>>> +             signal = llist_del_all(&b->signaled_requests);
>>>    
>>>        spin_lock(&b->irq_lock);
>>>    
>>> -     if (list_empty(&b->signalers))
>>> +     if (!signal && list_empty(&b->signalers))
>>
>> The only open from previous round was on this change. If I understood
>> your previous reply correctly, checking this or not simply controls the
>> disarm point and is not related to this patch. With the check added now
>> we would disarm later, because even already signaled requests would keep
>> it armed. I would prefer this was a separate patch if you could possibly
>> be convinced.
> 
> I considered that since we add to the lockless list and then queue the
> irq work, that is a path that is not driven by the interrupt and so
> causing an issue with the idea of the interrupt shadow. Having a simple
> test I thought was a positive side-effect to filter out the early
> irq_work.

I don't really follow. I look at it like this: No active signalers so we 
can disarm. What is the purpose of keeping the interrupt enabled if all 
that is on list are already completed requests? They will get signaled 
in the very same run of signal_irq_work so I don't see a connection with 
lockless list and keeping the interrupts on for longer.

Regards,

Tvrtko

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  parent reply	other threads:[~2020-07-31 15:32 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30  9:37 [Intel-gfx] Breadcrumbs fixes and stall avoidance Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 01/21] drm/i915: Add a couple of missing i915_active_fini() Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 02/21] drm/i915: Skip taking acquire mutex for no ref->active callback Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 03/21] drm/i915: Export a preallocate variant of i915_active_acquire() Chris Wilson
2020-07-31  7:33   ` Thomas Hellström (Intel)
2020-07-30  9:37 ` [Intel-gfx] [PATCH 04/21] drm/i915: Keep the most recently used active-fence upon discard Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 05/21] drm/i915: Make the stale cached active node available for any timeline Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 06/21] drm/i915: Reduce locking around i915_active_acquire_preallocate_barrier() Chris Wilson
2020-07-31  7:39   ` Thomas Hellström (Intel)
2020-07-30  9:37 ` [Intel-gfx] [PATCH 07/21] drm/i915: Provide a fastpath for waiting on vma bindings Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 08/21] drm/i915/gem: Reduce ctx->engine_mutex for reading the clone source Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 09/21] drm/i915/gem: Reduce ctx->engines_mutex for get_engines() Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 10/21] drm/i915: Remove requirement for holding i915_request.lock for breadcrumbs Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 11/21] drm/i915/gt: Replace intel_engine_transfer_stale_breadcrumbs Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 12/21] drm/i915/gt: Only transfer the virtual context to the new engine if active Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 13/21] drm/i915/gt: Distinguish the virtual breadcrumbs from the irq breadcrumbs Chris Wilson
2020-07-31 14:53   ` Tvrtko Ursulin
2020-07-30  9:37 ` [Intel-gfx] [PATCH 14/21] drm/i915/gt: Move intel_breadcrumbs_arm_irq earlier Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 15/21] drm/i915/gt: Hold context/request reference while breadcrumbs are active Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 16/21] drm/i915/gt: Track signaled breadcrumbs outside of the breadcrumb spinlock Chris Wilson
2020-07-31 15:06   ` Tvrtko Ursulin
2020-07-31 15:12     ` Chris Wilson
2020-07-31 15:21       ` Chris Wilson
2020-07-31 16:06         ` Tvrtko Ursulin
2020-07-31 17:59           ` Chris Wilson
2020-07-31 15:32       ` Tvrtko Ursulin [this message]
2020-07-30  9:37 ` [Intel-gfx] [PATCH 17/21] drm/i915/gt: Protect context lifetime with RCU Chris Wilson
2020-07-31 15:15   ` Tvrtko Ursulin
2020-07-31 15:24     ` Chris Wilson
2020-07-31 15:45       ` Tvrtko Ursulin
2020-07-30  9:37 ` [Intel-gfx] [PATCH 18/21] drm/i915/gt: Split the breadcrumb spinlock between global and contexts Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 19/21] drm/i915: Drop i915_request.lock serialisation around await_start Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 20/21] drm/i915: Drop i915_request.lock requirement for intel_rps_boost() Chris Wilson
2020-07-30  9:37 ` [Intel-gfx] [PATCH 21/21] drm/i915/gem: Delay tracking the GEM context until it is registered Chris Wilson
2020-07-30  9:37   ` Chris Wilson
2020-07-30 13:45 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for series starting with [01/21] drm/i915: Add a couple of missing i915_active_fini() Patchwork
2020-07-30 13:46 ` [Intel-gfx] ✗ Fi.CI.SPARSE: " Patchwork
2020-07-30 14:04 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2020-07-30 19:20 ` [Intel-gfx] ✓ Fi.CI.IGT: " Patchwork

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