Re: [Intel-gfx] [PATCH 04/10] drm/i915: move intel_context slab to direct module init/exit

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 26/07/2021 17:20, Jason Ekstrand wrote:
> On Mon, Jul 26, 2021 at 11:08 AM Tvrtko Ursulin
> <tvrtko.ursulin@linux.intel.com> wrote:
>> On 26/07/2021 16:42, Jason Ekstrand wrote:
>>> On Mon, Jul 26, 2021 at 10:30 AM Jason Ekstrand <jason@jlekstrand.net> wrote:
>>>>
>>>> On Mon, Jul 26, 2021 at 3:35 AM Tvrtko Ursulin
>>>> <tvrtko.ursulin@linux.intel.com> wrote:
>>>>>
>>>>>
>>>>> On 23/07/2021 20:29, Daniel Vetter wrote:
>>>>>> With the global kmem_cache shrink infrastructure gone there's nothing
>>>>>> special and we can convert them over.
>>>>>>
>>>>>> I'm doing this split up into each patch because there's quite a bit of
>>>>>> noise with removing the static global.slab_ce to just a
>>>>>> slab_ce.
>>>>>>
>>>>>> Cc: Jason Ekstrand <jason@jlekstrand.net>
>>>>>> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
>>>>>> ---
>>>>>>     drivers/gpu/drm/i915/gt/intel_context.c | 25 ++++++++-----------------
>>>>>>     drivers/gpu/drm/i915/gt/intel_context.h |  3 +++
>>>>>>     drivers/gpu/drm/i915/i915_globals.c     |  2 --
>>>>>>     drivers/gpu/drm/i915/i915_globals.h     |  1 -
>>>>>>     drivers/gpu/drm/i915/i915_pci.c         |  2 ++
>>>>>>     5 files changed, 13 insertions(+), 20 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
>>>>>> index baa05fddd690..283382549a6f 100644
>>>>>> --- a/drivers/gpu/drm/i915/gt/intel_context.c
>>>>>> +++ b/drivers/gpu/drm/i915/gt/intel_context.c
>>>>>> @@ -7,7 +7,6 @@
>>>>>>     #include "gem/i915_gem_pm.h"
>>>>>>
>>>>>>     #include "i915_drv.h"
>>>>>> -#include "i915_globals.h"
>>>>>>     #include "i915_trace.h"
>>>>>>
>>>>>>     #include "intel_context.h"
>>>>>> @@ -15,14 +14,11 @@
>>>>>>     #include "intel_engine_pm.h"
>>>>>>     #include "intel_ring.h"
>>>>>>
>>>>>> -static struct i915_global_context {
>>>>>> -     struct i915_global base;
>>>>>> -     struct kmem_cache *slab_ce;
>>>>>> -} global;
>>>>>> +struct kmem_cache *slab_ce;
>>>>
>>>> Static?  With that,
>>>>
>>>> Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
>>>>
>>>>>>
>>>>>>     static struct intel_context *intel_context_alloc(void)
>>>>>>     {
>>>>>> -     return kmem_cache_zalloc(global.slab_ce, GFP_KERNEL);
>>>>>> +     return kmem_cache_zalloc(slab_ce, GFP_KERNEL);
>>>>>>     }
>>>>>>
>>>>>>     static void rcu_context_free(struct rcu_head *rcu)
>>>>>> @@ -30,7 +26,7 @@ static void rcu_context_free(struct rcu_head *rcu)
>>>>>>         struct intel_context *ce = container_of(rcu, typeof(*ce), rcu);
>>>>>>
>>>>>>         trace_intel_context_free(ce);
>>>>>> -     kmem_cache_free(global.slab_ce, ce);
>>>>>> +     kmem_cache_free(slab_ce, ce);
>>>>>>     }
>>>>>>
>>>>>>     void intel_context_free(struct intel_context *ce)
>>>>>> @@ -410,22 +406,17 @@ void intel_context_fini(struct intel_context *ce)
>>>>>>         i915_active_fini(&ce->active);
>>>>>>     }
>>>>>>
>>>>>> -static void i915_global_context_exit(void)
>>>>>> +void i915_context_module_exit(void)
>>>>>>     {
>>>>>> -     kmem_cache_destroy(global.slab_ce);
>>>>>> +     kmem_cache_destroy(slab_ce);
>>>>>>     }
>>>>>>
>>>>>> -static struct i915_global_context global = { {
>>>>>> -     .exit = i915_global_context_exit,
>>>>>> -} };
>>>>>> -
>>>>>> -int __init i915_global_context_init(void)
>>>>>> +int __init i915_context_module_init(void)
>>>>>>     {
>>>>>> -     global.slab_ce = KMEM_CACHE(intel_context, SLAB_HWCACHE_ALIGN);
>>>>>> -     if (!global.slab_ce)
>>>>>> +     slab_ce = KMEM_CACHE(intel_context, SLAB_HWCACHE_ALIGN);
>>>>>> +     if (!slab_ce)
>>>>>>                 return -ENOMEM;
>>>>>>
>>>>>> -     i915_global_register(&global.base);
>>>>>>         return 0;
>>>>>>     }
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
>>>>>> index 974ef85320c2..a0ca82e3c40d 100644
>>>>>> --- a/drivers/gpu/drm/i915/gt/intel_context.h
>>>>>> +++ b/drivers/gpu/drm/i915/gt/intel_context.h
>>>>>> @@ -30,6 +30,9 @@ void intel_context_init(struct intel_context *ce,
>>>>>>                         struct intel_engine_cs *engine);
>>>>>>     void intel_context_fini(struct intel_context *ce);
>>>>>>
>>>>>> +void i915_context_module_exit(void);
>>>>>> +int i915_context_module_init(void);
>>>>>> +
>>>>>>     struct intel_context *
>>>>>>     intel_context_create(struct intel_engine_cs *engine);
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/i915/i915_globals.c b/drivers/gpu/drm/i915/i915_globals.c
>>>>>> index 3de7cf22ec76..d36eb7dc40aa 100644
>>>>>> --- a/drivers/gpu/drm/i915/i915_globals.c
>>>>>> +++ b/drivers/gpu/drm/i915/i915_globals.c
>>>>>> @@ -7,7 +7,6 @@
>>>>>>     #include <linux/slab.h>
>>>>>>     #include <linux/workqueue.h>
>>>>>>
>>>>>> -#include "gem/i915_gem_context.h"
>>>>>>     #include "gem/i915_gem_object.h"
>>>>>>     #include "i915_globals.h"
>>>>>>     #include "i915_request.h"
>>>>>> @@ -32,7 +31,6 @@ static void __i915_globals_cleanup(void)
>>>>>>     }
>>>>>>
>>>>>>     static __initconst int (* const initfn[])(void) = {
>>>>>> -     i915_global_context_init,
>>>>>>         i915_global_gem_context_init,
>>>>>>         i915_global_objects_init,
>>>>>>         i915_global_request_init,
>>>>>> diff --git a/drivers/gpu/drm/i915/i915_globals.h b/drivers/gpu/drm/i915/i915_globals.h
>>>>>> index d80901ba75e3..60daa738a188 100644
>>>>>> --- a/drivers/gpu/drm/i915/i915_globals.h
>>>>>> +++ b/drivers/gpu/drm/i915/i915_globals.h
>>>>>> @@ -23,7 +23,6 @@ int i915_globals_init(void);
>>>>>>     void i915_globals_exit(void);
>>>>>>
>>>>>>     /* constructors */
>>>>>> -int i915_global_context_init(void);
>>>>>>     int i915_global_gem_context_init(void);
>>>>>>     int i915_global_objects_init(void);
>>>>>>     int i915_global_request_init(void);
>>>>>> diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
>>>>>> index f9527269e30a..266618157775 100644
>>>>>> --- a/drivers/gpu/drm/i915/i915_pci.c
>>>>>> +++ b/drivers/gpu/drm/i915/i915_pci.c
>>>>>> @@ -33,6 +33,7 @@
>>>>>>     #include "i915_active.h"
>>>>>>     #include "i915_buddy.h"
>>>>>>     #include "i915_drv.h"
>>>>>> +#include "gem/i915_gem_context.h"
>>>>>
>>>>> It's a bit ugly to go to a design where i915_pci.c has to include so
>>>>> many random parts of i915. IMO for a complex driver like i915,
>>>>> compartmentalizing so much knowledge about the internals was better
>>>>> inside the globals layer.
>>>>
>>>> I agree that i915_pci feels like the wrong place to put this but I
>>>> don't think that's so much because globals don't belong in i915_pci
>>>> but because i915_init/exit don't belong there.  Maybe, once this is
>>>> all said and done (or at the start of the series), we should move
>>>> i915_init/exit to i915_drv.c?  Of course, there's a bunch of PCI
>>>> probing stuff in i915_drv.c so..... yeah.... our organization is
>>>> pretty busted.
>>>
>>> To put a finer point on this, the new "design" is really to have a
>>> single flat list instead of two, one nested inside the other.  There's
>>> nothing wrong with that at all.  The fact that all this stuff now
>>> lives in i915_pci.c is ugly.  But, as I said, that's kind-of an
>>> accident of history because that's where i915_init() and i915_exit()
>>> currently live.  We should just move the lot to i915_drv.c.
>>
>> Hmm.. on one hand it does sounds better to move to i915_drv.c, but is it
>> just because all these new include directive are so visibly out of place
>> in i915_pci.c?
>>
>> Perhaps we need i915_module.c and then i915_globals is a completely fine
>> concept. Desired IMO even since we have to avoid globals in general
>> (multi-gpu) so it sticks out nicely that all that is allowed to be
>> global has a special place.
>>
>> And i915_drv.c can remain being about a driver instance as bound to one GPU.
> 
> Is i915_drv.c about a single instance bound to a single GPU?  If so,

Yep, all functions there either take drm_dev, pdev or dev_priv as 
argument, or return/initialize dev_priv.

> then, yeah, maybe not the right place.  Maybe a i915_module.c would be
> better.  It's all different shades of shed paint.

Hm not really just different shades IMO. Because I argue the patch 
series as is is a retrograde step in the above discussed respect.

I think i915_globals is cleaner code organisation. Because even if we 
add i915_module.c, then that can be made initialize globals and register 
with pci in cleanly separated steps without the need to include many 
driver internals.

I see r-b are accumulating but I hope reasonable objections will be 
considered.

Regards,

Tvrtko

> 
> --Jason
> 
>> That feels like the best of both worlds to me.
>>
>> Regards,
>>
>> Tvrtko
>>
>>>
>>>> --Jason
>>>>
>>>>> Maybe add a cover letter to explain the perceived pros and cons and
>>>>> thinking in general?
>>>>>
>>>>> Regards,
>>>>>
>>>>> Tvrtko
>>>>>
>>>>>>     #include "i915_perf.h"
>>>>>>     #include "i915_globals.h"
>>>>>>     #include "i915_selftest.h"
>>>>>> @@ -1297,6 +1298,7 @@ static const struct {
>>>>>>         { i915_check_nomodeset, NULL },
>>>>>>         { i915_active_module_init, i915_active_module_exit },
>>>>>>         { i915_buddy_module_init, i915_buddy_module_exit },
>>>>>> +     { i915_context_module_init, i915_context_module_exit },
>>>>>>         { i915_globals_init, i915_globals_exit },
>>>>>>         { i915_mock_selftests, NULL },
>>>>>>         { i915_pmu_init, i915_pmu_exit },
>>>>>>
>>>>> _______________________________________________
>>>>> Intel-gfx mailing list
>>>>> Intel-gfx@lists.freedesktop.org
>>>>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
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