Re: [Intel-gfx] [PATCH 1/2 v2] drm/i915: mark GEM object pages dirty when mapped & written by the CPU
On Fri, Dec 11, 2015 at 06:08:10PM +0100, Daniel Vetter wrote: > Hm, I think if you force a fault on relocs and then shrink everything > really hard before actually managing to submit the batch you could provoke > this into a proper bug. one-in-a-billion perhaps ;-) Hmm, you would need to force the slowpath (otherwise all the objects are reserved and so not swappable). And then we force the presumed_offset to be invalid but only on the user side - so we don't force the relocations in this batch. Ok, plausible. But who hits the slowpath? Sigh. Fancy reviewing some mesa patches? -Chris -- Chris Wilson, Intel Open Source Technology Centre ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
Re: [Intel-gfx] [PATCH 1/2 v2] drm/i915: mark GEM object pages dirty when mapped & written by the CPU
On Thu, Dec 10, 2015 at 09:04:23PM +, Chris Wilson wrote: > On Thu, Dec 10, 2015 at 05:24:42PM +, Dave Gordon wrote: > > On 10/12/15 13:29, Chris Wilson wrote: > > >On Wed, Dec 09, 2015 at 03:52:51PM +, Dave Gordon wrote: > > >>In various places, a single page of a (regular) GEM object is mapped into > > >>CPU address space and updated. In each such case, either the page or the > > >>the object should be marked dirty, to ensure that the modifications are > > >>not discarded if the object is evicted under memory pressure. > > >> > > >>The typical sequence is: > > >> va = kmap_atomic(i915_gem_object_get_page(obj, pageno)); > > >> *(va+offset) = ... > > >> kunmap_atomic(va); > > >> > > >>Here we introduce i915_gem_object_get_dirty_page(), which performs the > > >>same operation as i915_gem_object_get_page() but with the side-effect > > >>of marking the returned page dirty in the pagecache. This will ensure > > >>that if the object is subsequently evicted (due to memory pressure), > > >>the changes are written to backing store rather than discarded. > > >> > > >>Note that it works only for regular (shmfs-backed) GEM objects, but (at > > >>least for now) those are the only ones that are updated in this way -- > > >>the objects in question are contexts and batchbuffers, which are always > > >>shmfs-backed. > > >> > > >>A separate patch deals with the case where whole objects are (or may > > >>be) dirtied. > > >> > > >>Signed-off-by: Dave Gordon > > >>Cc: Chris Wilson > > > > > >I like this. There are places were we do both obj->dirty and > > >set_page_dirty(), but this so much more clearly shows what is going on. > > >All of these locations should be infrequent (or at least have patches to > > >make them so), so moving the call out-of-line will also be a benefit. > > > > I think there was only one place that both called set_page_dirty() > > AND set obj->dirty, which was in populate_lr_context(). You'll see > > that I've eliminated both in favour of a call to get_dirty_page() :) > > It was things like all GPU objects have obj->dirty set, so really the > importance of using get_dirty_page() in the relocations and context > pinning is for documentation. Which is a very good reason, nevertheless. Hm, I think if you force a fault on relocs and then shrink everything really hard before actually managing to submit the batch you could provoke this into a proper bug. one-in-a-billion perhaps ;-) -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
Re: [Intel-gfx] [PATCH 1/2 v2] drm/i915: mark GEM object pages dirty when mapped & written by the CPU
On Thu, Dec 10, 2015 at 05:24:42PM +, Dave Gordon wrote: > On 10/12/15 13:29, Chris Wilson wrote: > >On Wed, Dec 09, 2015 at 03:52:51PM +, Dave Gordon wrote: > >>In various places, a single page of a (regular) GEM object is mapped into > >>CPU address space and updated. In each such case, either the page or the > >>the object should be marked dirty, to ensure that the modifications are > >>not discarded if the object is evicted under memory pressure. > >> > >>The typical sequence is: > >>va = kmap_atomic(i915_gem_object_get_page(obj, pageno)); > >>*(va+offset) = ... > >>kunmap_atomic(va); > >> > >>Here we introduce i915_gem_object_get_dirty_page(), which performs the > >>same operation as i915_gem_object_get_page() but with the side-effect > >>of marking the returned page dirty in the pagecache. This will ensure > >>that if the object is subsequently evicted (due to memory pressure), > >>the changes are written to backing store rather than discarded. > >> > >>Note that it works only for regular (shmfs-backed) GEM objects, but (at > >>least for now) those are the only ones that are updated in this way -- > >>the objects in question are contexts and batchbuffers, which are always > >>shmfs-backed. > >> > >>A separate patch deals with the case where whole objects are (or may > >>be) dirtied. > >> > >>Signed-off-by: Dave Gordon > >>Cc: Chris Wilson > > > >I like this. There are places were we do both obj->dirty and > >set_page_dirty(), but this so much more clearly shows what is going on. > >All of these locations should be infrequent (or at least have patches to > >make them so), so moving the call out-of-line will also be a benefit. > > I think there was only one place that both called set_page_dirty() > AND set obj->dirty, which was in populate_lr_context(). You'll see > that I've eliminated both in favour of a call to get_dirty_page() :) It was things like all GPU objects have obj->dirty set, so really the importance of using get_dirty_page() in the relocations and context pinning is for documentation. Which is a very good reason, nevertheless. -Chris -- Chris Wilson, Intel Open Source Technology Centre ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
Re: [Intel-gfx] [PATCH 1/2 v2] drm/i915: mark GEM object pages dirty when mapped & written by the CPU
On 10/12/15 13:29, Chris Wilson wrote: On Wed, Dec 09, 2015 at 03:52:51PM +, Dave Gordon wrote: In various places, a single page of a (regular) GEM object is mapped into CPU address space and updated. In each such case, either the page or the the object should be marked dirty, to ensure that the modifications are not discarded if the object is evicted under memory pressure. The typical sequence is: va = kmap_atomic(i915_gem_object_get_page(obj, pageno)); *(va+offset) = ... kunmap_atomic(va); Here we introduce i915_gem_object_get_dirty_page(), which performs the same operation as i915_gem_object_get_page() but with the side-effect of marking the returned page dirty in the pagecache. This will ensure that if the object is subsequently evicted (due to memory pressure), the changes are written to backing store rather than discarded. Note that it works only for regular (shmfs-backed) GEM objects, but (at least for now) those are the only ones that are updated in this way -- the objects in question are contexts and batchbuffers, which are always shmfs-backed. A separate patch deals with the case where whole objects are (or may be) dirtied. Signed-off-by: Dave Gordon Cc: Chris Wilson I like this. There are places were we do both obj->dirty and set_page_dirty(), but this so much more clearly shows what is going on. All of these locations should be infrequent (or at least have patches to make them so), so moving the call out-of-line will also be a benefit. I think there was only one place that both called set_page_dirty() AND set obj->dirty, which was in populate_lr_context(). You'll see that I've eliminated both in favour of a call to get_dirty_page() :) /* Allocate a new GEM object and fill it with the supplied data */ struct drm_i915_gem_object * i915_gem_object_create_from_data(struct drm_device *dev, diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c index a4c243c..81796cc 100644 --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c @@ -264,7 +264,7 @@ relocate_entry_cpu(struct drm_i915_gem_object *obj, if (ret) return ret; - vaddr = kmap_atomic(i915_gem_object_get_page(obj, + vaddr = kmap_atomic(i915_gem_object_get_dirty_page(obj, reloc->offset >> PAGE_SHIFT)); *(uint32_t *)(vaddr + page_offset) = lower_32_bits(delta); @@ -355,7 +355,7 @@ relocate_entry_clflush(struct drm_i915_gem_object *obj, if (ret) return ret; - vaddr = kmap_atomic(i915_gem_object_get_page(obj, + vaddr = kmap_atomic(i915_gem_object_get_dirty_page(obj, reloc->offset >> PAGE_SHIFT)); clflush_write32(vaddr + page_offset, lower_32_bits(delta)); The relocation functions may dirty pairs of pages. Other than that, I think you have the right mix of callsites. -Chris Thanks, I've added the other two to the next (v3) version :) .Dave. ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
Re: [Intel-gfx] [PATCH 1/2 v2] drm/i915: mark GEM object pages dirty when mapped & written by the CPU
On Wed, Dec 09, 2015 at 03:52:51PM +, Dave Gordon wrote: > In various places, a single page of a (regular) GEM object is mapped into > CPU address space and updated. In each such case, either the page or the > the object should be marked dirty, to ensure that the modifications are > not discarded if the object is evicted under memory pressure. > > The typical sequence is: > va = kmap_atomic(i915_gem_object_get_page(obj, pageno)); > *(va+offset) = ... > kunmap_atomic(va); > > Here we introduce i915_gem_object_get_dirty_page(), which performs the > same operation as i915_gem_object_get_page() but with the side-effect > of marking the returned page dirty in the pagecache. This will ensure > that if the object is subsequently evicted (due to memory pressure), > the changes are written to backing store rather than discarded. > > Note that it works only for regular (shmfs-backed) GEM objects, but (at > least for now) those are the only ones that are updated in this way -- > the objects in question are contexts and batchbuffers, which are always > shmfs-backed. > > A separate patch deals with the case where whole objects are (or may > be) dirtied. > > Signed-off-by: Dave Gordon > Cc: Chris Wilson I like this. There are places were we do both obj->dirty and set_page_dirty(), but this so much more clearly shows what is going on. All of these locations should be infrequent (or at least have patches to make them so), so moving the call out-of-line will also be a benefit. > /* Allocate a new GEM object and fill it with the supplied data */ > struct drm_i915_gem_object * > i915_gem_object_create_from_data(struct drm_device *dev, > diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c > b/drivers/gpu/drm/i915/i915_gem_execbuffer.c > index a4c243c..81796cc 100644 > --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c > +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c > @@ -264,7 +264,7 @@ relocate_entry_cpu(struct drm_i915_gem_object *obj, > if (ret) > return ret; > > - vaddr = kmap_atomic(i915_gem_object_get_page(obj, > + vaddr = kmap_atomic(i915_gem_object_get_dirty_page(obj, > reloc->offset >> PAGE_SHIFT)); > *(uint32_t *)(vaddr + page_offset) = lower_32_bits(delta); > > @@ -355,7 +355,7 @@ relocate_entry_clflush(struct drm_i915_gem_object *obj, > if (ret) > return ret; > > - vaddr = kmap_atomic(i915_gem_object_get_page(obj, > + vaddr = kmap_atomic(i915_gem_object_get_dirty_page(obj, > reloc->offset >> PAGE_SHIFT)); > clflush_write32(vaddr + page_offset, lower_32_bits(delta)); > The relocation functions may dirty pairs of pages. Other than that, I think you have the right mix of callsites. -Chris -- Chris Wilson, Intel Open Source Technology Centre ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
