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

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On 26/07/2021 16:42, Jason Ekstrand wrote:
On Mon, Jul 26, 2021 at 10:30 AM Jason Ekstrand <jason@xxxxxxxxxxxxxx> wrote:

On Mon, Jul 26, 2021 at 3:35 AM Tvrtko Ursulin
<tvrtko.ursulin@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
---
   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@xxxxxxxxxxxxxx>


   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.

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 },

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