[Nouveau] [PATCH 2/2] nouveau: Do not add most bo's to the global bo list.

[Patrick Baggett]

On Wed, Feb 25, 2015 at 8:59 AM, Maarten Lankhorst <
maarten.lankhorst at ubuntu.com> wrote:

> Op 25-02-15 om 15:11 schreef Emil Velikov:
> > On 24 February 2015 at 09:01, Maarten Lankhorst
> > <maarten.lankhorst at ubuntu.com> wrote:
> >> Only add wrapped bo's and bo's that have been exported through flink or
> dma-buf.
> >> This avoids a lock in the common case, and decreases traversal needed
> for importing
> >> a dma-buf or flink.
> >>
> >> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at ubuntu.com>
> >> ---
> >>  nouveau/nouveau.c | 47 +++++++++++++++++++++++------------------------
> >>  1 file changed, 23 insertions(+), 24 deletions(-)
> >>
> >> diff --git a/nouveau/nouveau.c b/nouveau/nouveau.c
> >> index 1c723b9..d411523 100644
> >> --- a/nouveau/nouveau.c
> >> +++ b/nouveau/nouveau.c
> >> @@ -349,8 +349,8 @@ nouveau_bo_del(struct nouveau_bo *bo)
> >>         struct nouveau_bo_priv *nvbo = nouveau_bo(bo);
> >>         struct drm_gem_close req = { bo->handle };
> >>
> >> -       pthread_mutex_lock(&nvdev->lock);
> >> -       if (nvbo->name) {
> >> +       if (nvbo->head.next) {
> >> +               pthread_mutex_lock(&nvdev->lock);
> >>                 if (atomic_read(&nvbo->refcnt) == 0) {
> >>                         DRMLISTDEL(&nvbo->head);
> >>                         /*
> >> @@ -365,8 +365,6 @@ nouveau_bo_del(struct nouveau_bo *bo)
> >>                 }
> >>                 pthread_mutex_unlock(&nvdev->lock);
> >>         } else {
> >> -               DRMLISTDEL(&nvbo->head);
> >> -               pthread_mutex_unlock(&nvdev->lock);
> >>                 drmIoctl(bo->device->fd, DRM_IOCTL_GEM_CLOSE, &req);
> >>         }
> >>         if (bo->map)
> >> @@ -379,7 +377,6 @@ nouveau_bo_new(struct nouveau_device *dev, uint32_t
> flags, uint32_t align,
> >>                uint64_t size, union nouveau_bo_config *config,
> >>                struct nouveau_bo **pbo)
> >>  {
> >> -       struct nouveau_device_priv *nvdev = nouveau_device(dev);
> >>         struct nouveau_bo_priv *nvbo = calloc(1, sizeof(*nvbo));
> >>         struct nouveau_bo *bo = &nvbo->base;
> >>         int ret;
> >> @@ -397,10 +394,6 @@ nouveau_bo_new(struct nouveau_device *dev,
> uint32_t flags, uint32_t align,
> >>                 return ret;
> >>         }
> >>
> >> -       pthread_mutex_lock(&nvdev->lock);
> >> -       DRMLISTADD(&nvbo->head, &nvdev->bo_list);
> >> -       pthread_mutex_unlock(&nvdev->lock);
> >> -
> >>         *pbo = bo;
> >>         return 0;
> >>  }
> >> @@ -457,6 +450,18 @@ nouveau_bo_wrap_locked(struct nouveau_device *dev,
> uint32_t handle,
> >>         return -ENOMEM;
> >>  }
> >>
> >> +static void
> >> +nouveau_bo_make_global(struct nouveau_bo_priv *nvbo)
> >> +{
> >> +       if (!nvbo->head.next) {
> >> +               struct nouveau_device_priv *nvdev =
> nouveau_device(nvbo->base.device);
> >> +               pthread_mutex_lock(&nvdev->lock);
> >> +               if (!nvbo->head.next)
>
I guess the bo_make_global call is not particularly sensitive, so
> removing's fine with me.
>
I would be worried about the duplicated check. It seems like a "smart"
compiler could cache the value of "nvbo->head.next" (unless marked as
volatile), rendering the second if() useless. If the field is marked
volatile, then of course, this does not apply.

-Patrick

>
> ~Maarten
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