[PATCH 3/4] drm/ttm, drm/vmwgfx: Use RCU locking for object lookups v3
On Tue, Nov 20, 2012 at 4:44 PM, Thomas Hellstrom wrote: > On 11/20/2012 07:19 AM, Dave Airlie wrote: >> >> On Tue, Nov 6, 2012 at 9:31 PM, Thomas Hellstrom >> wrote: >>> >>> The mostly used lookup+get put+potential_destroy path of TTM objects >>> is converted to use RCU locks. This will substantially decrease the >>> amount >>> of locked bus cycles during normal operation. >>> Since we use kfree_rcu to free the objects, no rcu synchronization is >>> needed >>> at module unload time. >> >> As this is the first use of RCU in a drm driver from what I can see, >> let me remind that the >> RCU patent agreement AFAIK only covers GPL works. >> >> So non-GPL or other OSes porting this code should take not of this. >> >> Dave. > > > From VMware's side this won't be a problem, since other VMware kernel > modules (VMCI IIRC) use RCU. > > In any case I have a new version of the "vmwgfx optimization" patch series > that mostly add documentation and > annotation (by using a drm_ht_xxx_rcu) interface for hashtab, after an > internal review by Dmitry Torkov. I see you've already > applied the original patch series. Do you want me to send out the new one or > rebase it against current drm-next? Can you rebase it on top of -next? Dave.
[PATCH 3/4] drm/ttm, drm/vmwgfx: Use RCU locking for object lookups v3
On Tue, Nov 6, 2012 at 9:31 PM, Thomas Hellstrom wrote: > The mostly used lookup+get put+potential_destroy path of TTM objects > is converted to use RCU locks. This will substantially decrease the amount > of locked bus cycles during normal operation. > Since we use kfree_rcu to free the objects, no rcu synchronization is needed > at module unload time. As this is the first use of RCU in a drm driver from what I can see, let me remind that the RCU patent agreement AFAIK only covers GPL works. So non-GPL or other OSes porting this code should take not of this. Dave.
[PATCH 3/4] drm/ttm, drm/vmwgfx: Use RCU locking for object lookups v3
On 11/20/2012 07:19 AM, Dave Airlie wrote: > On Tue, Nov 6, 2012 at 9:31 PM, Thomas Hellstrom > wrote: >> The mostly used lookup+get put+potential_destroy path of TTM objects >> is converted to use RCU locks. This will substantially decrease the amount >> of locked bus cycles during normal operation. >> Since we use kfree_rcu to free the objects, no rcu synchronization is needed >> at module unload time. > As this is the first use of RCU in a drm driver from what I can see, > let me remind that the > RCU patent agreement AFAIK only covers GPL works. > > So non-GPL or other OSes porting this code should take not of this. > > Dave. From VMware's side this won't be a problem, since other VMware kernel modules (VMCI IIRC) use RCU. In any case I have a new version of the "vmwgfx optimization" patch series that mostly add documentation and annotation (by using a drm_ht_xxx_rcu) interface for hashtab, after an internal review by Dmitry Torkov. I see you've already applied the original patch series. Do you want me to send out the new one or rebase it against current drm-next? Thanks, Thomas
Re: [PATCH 3/4] drm/ttm, drm/vmwgfx: Use RCU locking for object lookups v3
On Tue, Nov 20, 2012 at 4:44 PM, Thomas Hellstrom thellst...@vmware.com wrote: On 11/20/2012 07:19 AM, Dave Airlie wrote: On Tue, Nov 6, 2012 at 9:31 PM, Thomas Hellstrom thellst...@vmware.com wrote: The mostly used lookup+get put+potential_destroy path of TTM objects is converted to use RCU locks. This will substantially decrease the amount of locked bus cycles during normal operation. Since we use kfree_rcu to free the objects, no rcu synchronization is needed at module unload time. As this is the first use of RCU in a drm driver from what I can see, let me remind that the RCU patent agreement AFAIK only covers GPL works. So non-GPL or other OSes porting this code should take not of this. Dave. From VMware's side this won't be a problem, since other VMware kernel modules (VMCI IIRC) use RCU. In any case I have a new version of the vmwgfx optimization patch series that mostly add documentation and annotation (by using a drm_ht_xxx_rcu) interface for hashtab, after an internal review by Dmitry Torkov. I see you've already applied the original patch series. Do you want me to send out the new one or rebase it against current drm-next? Can you rebase it on top of -next? Dave. ___ dri-devel mailing list dri-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH 3/4] drm/ttm, drm/vmwgfx: Use RCU locking for object lookups v3
On Tue, Nov 6, 2012 at 9:31 PM, Thomas Hellstrom thellst...@vmware.com wrote: The mostly used lookup+get put+potential_destroy path of TTM objects is converted to use RCU locks. This will substantially decrease the amount of locked bus cycles during normal operation. Since we use kfree_rcu to free the objects, no rcu synchronization is needed at module unload time. As this is the first use of RCU in a drm driver from what I can see, let me remind that the RCU patent agreement AFAIK only covers GPL works. So non-GPL or other OSes porting this code should take not of this. Dave. ___ dri-devel mailing list dri-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH 3/4] drm/ttm, drm/vmwgfx: Use RCU locking for object lookups v3
On 11/20/2012 07:19 AM, Dave Airlie wrote: On Tue, Nov 6, 2012 at 9:31 PM, Thomas Hellstrom thellst...@vmware.com wrote: The mostly used lookup+get put+potential_destroy path of TTM objects is converted to use RCU locks. This will substantially decrease the amount of locked bus cycles during normal operation. Since we use kfree_rcu to free the objects, no rcu synchronization is needed at module unload time. As this is the first use of RCU in a drm driver from what I can see, let me remind that the RCU patent agreement AFAIK only covers GPL works. So non-GPL or other OSes porting this code should take not of this. Dave. From VMware's side this won't be a problem, since other VMware kernel modules (VMCI IIRC) use RCU. In any case I have a new version of the vmwgfx optimization patch series that mostly add documentation and annotation (by using a drm_ht_xxx_rcu) interface for hashtab, after an internal review by Dmitry Torkov. I see you've already applied the original patch series. Do you want me to send out the new one or rebase it against current drm-next? Thanks, Thomas ___ dri-devel mailing list dri-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/dri-devel
[PATCH 3/4] drm/ttm, drm/vmwgfx: Use RCU locking for object lookups v3
The mostly used lookup+get put+potential_destroy path of TTM objects is converted to use RCU locks. This will substantially decrease the amount of locked bus cycles during normal operation. Since we use kfree_rcu to free the objects, no rcu synchronization is needed at module unload time. v2: Don't touch include/linux/kref.h v3: Adapt to kref_get_unless_zero return value change Signed-off-by: Thomas Hellstrom --- drivers/gpu/drm/ttm/ttm_object.c | 30 +++--- drivers/gpu/drm/vmwgfx/vmwgfx_resource.c |8 include/drm/ttm/ttm_object.h |4 3 files changed, 19 insertions(+), 23 deletions(-) diff --git a/drivers/gpu/drm/ttm/ttm_object.c b/drivers/gpu/drm/ttm/ttm_object.c index c785787..f18eeb4 100644 --- a/drivers/gpu/drm/ttm/ttm_object.c +++ b/drivers/gpu/drm/ttm/ttm_object.c @@ -80,7 +80,7 @@ struct ttm_object_file { */ struct ttm_object_device { - rwlock_t object_lock; + spinlock_t object_lock; struct drm_open_hash object_hash; atomic_t object_count; struct ttm_mem_global *mem_glob; @@ -157,12 +157,12 @@ int ttm_base_object_init(struct ttm_object_file *tfile, base->refcount_release = refcount_release; base->ref_obj_release = ref_obj_release; base->object_type = object_type; - write_lock(>object_lock); + spin_lock(>object_lock); kref_init(>refcount); ret = drm_ht_just_insert_please(>object_hash, >hash, (unsigned long)base, 31, 0, 0); - write_unlock(>object_lock); + spin_unlock(>object_lock); if (unlikely(ret != 0)) goto out_err0; @@ -186,30 +186,22 @@ static void ttm_release_base(struct kref *kref) container_of(kref, struct ttm_base_object, refcount); struct ttm_object_device *tdev = base->tfile->tdev; + spin_lock(>object_lock); (void)drm_ht_remove_item(>object_hash, >hash); - write_unlock(>object_lock); + spin_unlock(>object_lock); if (base->refcount_release) { ttm_object_file_unref(>tfile); base->refcount_release(); } - write_lock(>object_lock); } void ttm_base_object_unref(struct ttm_base_object **p_base) { struct ttm_base_object *base = *p_base; - struct ttm_object_device *tdev = base->tfile->tdev; *p_base = NULL; - /* -* Need to take the lock here to avoid racing with -* users trying to look up the object. -*/ - - write_lock(>object_lock); kref_put(>refcount, ttm_release_base); - write_unlock(>object_lock); } EXPORT_SYMBOL(ttm_base_object_unref); @@ -221,14 +213,14 @@ struct ttm_base_object *ttm_base_object_lookup(struct ttm_object_file *tfile, struct drm_hash_item *hash; int ret; - read_lock(>object_lock); + rcu_read_lock(); ret = drm_ht_find_item(>object_hash, key, ); if (likely(ret == 0)) { base = drm_hash_entry(hash, struct ttm_base_object, hash); - kref_get(>refcount); + ret = kref_get_unless_zero(>refcount) ? 0 : -EINVAL; } - read_unlock(>object_lock); + rcu_read_unlock(); if (unlikely(ret != 0)) return NULL; @@ -426,7 +418,7 @@ struct ttm_object_device *ttm_object_device_init(struct ttm_mem_global return NULL; tdev->mem_glob = mem_glob; - rwlock_init(>object_lock); + spin_lock_init(>object_lock); atomic_set(>object_count, 0); ret = drm_ht_create(>object_hash, hash_order); @@ -444,9 +436,9 @@ void ttm_object_device_release(struct ttm_object_device **p_tdev) *p_tdev = NULL; - write_lock(>object_lock); + spin_lock(>object_lock); drm_ht_remove(>object_hash); - write_unlock(>object_lock); + spin_unlock(>object_lock); kfree(tdev); } diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c index da3c6b5..ae675c6 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c @@ -351,7 +351,7 @@ static void vmw_user_context_free(struct vmw_resource *res) container_of(res, struct vmw_user_context, res); struct vmw_private *dev_priv = res->dev_priv; - kfree(ctx); + ttm_base_object_kfree(ctx, base); ttm_mem_global_free(vmw_mem_glob(dev_priv), vmw_user_context_size); } @@ -1147,7 +1147,7 @@ static void vmw_user_surface_free(struct vmw_resource *res) kfree(srf->offsets); kfree(srf->sizes); kfree(srf->snooper.image); - kfree(user_srf); + ttm_base_object_kfree(user_srf, base); ttm_mem_global_free(vmw_mem_glob(dev_priv), size); } @@ -1575,7 +1575,7 @@ static void vmw_user_dmabuf_destroy(struct ttm_buffer_object *bo) {
[PATCH 3/4] drm/ttm, drm/vmwgfx: Use RCU locking for object lookups v3
The mostly used lookup+get put+potential_destroy path of TTM objects is converted to use RCU locks. This will substantially decrease the amount of locked bus cycles during normal operation. Since we use kfree_rcu to free the objects, no rcu synchronization is needed at module unload time. v2: Don't touch include/linux/kref.h v3: Adapt to kref_get_unless_zero return value change Signed-off-by: Thomas Hellstrom thellst...@vmware.com --- drivers/gpu/drm/ttm/ttm_object.c | 30 +++--- drivers/gpu/drm/vmwgfx/vmwgfx_resource.c |8 include/drm/ttm/ttm_object.h |4 3 files changed, 19 insertions(+), 23 deletions(-) diff --git a/drivers/gpu/drm/ttm/ttm_object.c b/drivers/gpu/drm/ttm/ttm_object.c index c785787..f18eeb4 100644 --- a/drivers/gpu/drm/ttm/ttm_object.c +++ b/drivers/gpu/drm/ttm/ttm_object.c @@ -80,7 +80,7 @@ struct ttm_object_file { */ struct ttm_object_device { - rwlock_t object_lock; + spinlock_t object_lock; struct drm_open_hash object_hash; atomic_t object_count; struct ttm_mem_global *mem_glob; @@ -157,12 +157,12 @@ int ttm_base_object_init(struct ttm_object_file *tfile, base-refcount_release = refcount_release; base-ref_obj_release = ref_obj_release; base-object_type = object_type; - write_lock(tdev-object_lock); + spin_lock(tdev-object_lock); kref_init(base-refcount); ret = drm_ht_just_insert_please(tdev-object_hash, base-hash, (unsigned long)base, 31, 0, 0); - write_unlock(tdev-object_lock); + spin_unlock(tdev-object_lock); if (unlikely(ret != 0)) goto out_err0; @@ -186,30 +186,22 @@ static void ttm_release_base(struct kref *kref) container_of(kref, struct ttm_base_object, refcount); struct ttm_object_device *tdev = base-tfile-tdev; + spin_lock(tdev-object_lock); (void)drm_ht_remove_item(tdev-object_hash, base-hash); - write_unlock(tdev-object_lock); + spin_unlock(tdev-object_lock); if (base-refcount_release) { ttm_object_file_unref(base-tfile); base-refcount_release(base); } - write_lock(tdev-object_lock); } void ttm_base_object_unref(struct ttm_base_object **p_base) { struct ttm_base_object *base = *p_base; - struct ttm_object_device *tdev = base-tfile-tdev; *p_base = NULL; - /* -* Need to take the lock here to avoid racing with -* users trying to look up the object. -*/ - - write_lock(tdev-object_lock); kref_put(base-refcount, ttm_release_base); - write_unlock(tdev-object_lock); } EXPORT_SYMBOL(ttm_base_object_unref); @@ -221,14 +213,14 @@ struct ttm_base_object *ttm_base_object_lookup(struct ttm_object_file *tfile, struct drm_hash_item *hash; int ret; - read_lock(tdev-object_lock); + rcu_read_lock(); ret = drm_ht_find_item(tdev-object_hash, key, hash); if (likely(ret == 0)) { base = drm_hash_entry(hash, struct ttm_base_object, hash); - kref_get(base-refcount); + ret = kref_get_unless_zero(base-refcount) ? 0 : -EINVAL; } - read_unlock(tdev-object_lock); + rcu_read_unlock(); if (unlikely(ret != 0)) return NULL; @@ -426,7 +418,7 @@ struct ttm_object_device *ttm_object_device_init(struct ttm_mem_global return NULL; tdev-mem_glob = mem_glob; - rwlock_init(tdev-object_lock); + spin_lock_init(tdev-object_lock); atomic_set(tdev-object_count, 0); ret = drm_ht_create(tdev-object_hash, hash_order); @@ -444,9 +436,9 @@ void ttm_object_device_release(struct ttm_object_device **p_tdev) *p_tdev = NULL; - write_lock(tdev-object_lock); + spin_lock(tdev-object_lock); drm_ht_remove(tdev-object_hash); - write_unlock(tdev-object_lock); + spin_unlock(tdev-object_lock); kfree(tdev); } diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c index da3c6b5..ae675c6 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c @@ -351,7 +351,7 @@ static void vmw_user_context_free(struct vmw_resource *res) container_of(res, struct vmw_user_context, res); struct vmw_private *dev_priv = res-dev_priv; - kfree(ctx); + ttm_base_object_kfree(ctx, base); ttm_mem_global_free(vmw_mem_glob(dev_priv), vmw_user_context_size); } @@ -1147,7 +1147,7 @@ static void vmw_user_surface_free(struct vmw_resource *res) kfree(srf-offsets); kfree(srf-sizes); kfree(srf-snooper.image); - kfree(user_srf); + ttm_base_object_kfree(user_srf, base);