[PATCH 1/2] dma-buf: start caching of sg_table objects v2
Daniel Vetter
daniel at ffwll.ch
Wed May 22 08:11:37 UTC 2019
On Thu, May 16, 2019 at 08:26:36AM +0200, Daniel Vetter wrote:
> On Wed, May 15, 2019 at 11:25 AM Christian König
> <ckoenig.leichtzumerken at gmail.com> wrote:
> >
> > Am 15.05.19 um 10:58 schrieb Daniel Vetter:
> > > On Tue, May 14, 2019 at 04:05:14PM +0200, Christian König wrote:
> > >> To allow a smooth transition from pinning buffer objects to dynamic
> > >> invalidation we first start to cache the sg_table for an attachment.
> > >>
> > >> v2: keep closer to the DRM implementation
> > >>
> > >> Signed-off-by: Christian König <christian.koenig at amd.com>
> > > i915 doesn't use the prime helpers, so this would be a change for us.
> >
> > Not a problem at all, see below. I've added an cache_sgt_mapping member
> > into the dma_buf_ops structure. Only when this member is true the
> > functionality is enabled.
>
> Hm right I missed that.
>
> > So I'm just moving code around in those two patches and no functional
> > change at all.
>
> Still not sure. I'll look at your latest dma-buf series to see how it
> all fits together.
Ok I'm still procrastinating on that one, but I guess either way we need
some caching or another in dma-buf.c, and this series here at least looks
like it's moving in that direction.
On both patches Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
btw might be good to throw this at intel-gfx-trybot too, just to see
whether anything is amiss. I think we've beaten down all the -rc1
regressions now.
-Daniel
> -Daniel
>
> >
> > Regards,
> > Christian.
> >
> > > Not
> > > sure that matters. Since we can't use this as an easy way out of the
> > > locking problem around reservation_object I'm not sure how useful it is to
> > > move this ahead. At least until we have a clearer picture on how we plan
> > > to roll out the dynamic dma-buf stuff. Once we have a bit more clarity
> > > there I'm all for merging prep work, but as-is I'd be cautious ... This
> > > stuff is a lot more tricky than it seems at first :-/
> > > -Daniel
> > >> ---
> > >> drivers/dma-buf/dma-buf.c | 27 +++++++++++++++++++++++++--
> > >> include/linux/dma-buf.h | 13 +++++++++++++
> > >> 2 files changed, 38 insertions(+), 2 deletions(-)
> > >>
> > >> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> > >> index 7c858020d14b..a2d34c6b80a5 100644
> > >> --- a/drivers/dma-buf/dma-buf.c
> > >> +++ b/drivers/dma-buf/dma-buf.c
> > >> @@ -573,6 +573,7 @@ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
> > >> list_add(&attach->node, &dmabuf->attachments);
> > >>
> > >> mutex_unlock(&dmabuf->lock);
> > >> +
> > >> return attach;
> > >>
> > >> err_attach:
> > >> @@ -595,6 +596,9 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
> > >> if (WARN_ON(!dmabuf || !attach))
> > >> return;
> > >>
> > >> + if (attach->sgt)
> > >> + dmabuf->ops->unmap_dma_buf(attach, attach->sgt, attach->dir);
> > >> +
> > >> mutex_lock(&dmabuf->lock);
> > >> list_del(&attach->node);
> > >> if (dmabuf->ops->detach)
> > >> @@ -630,10 +634,27 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> > >> if (WARN_ON(!attach || !attach->dmabuf))
> > >> return ERR_PTR(-EINVAL);
> > >>
> > >> + if (attach->sgt) {
> > >> + /*
> > >> + * Two mappings with different directions for the same
> > >> + * attachment are not allowed.
> > >> + */
> > >> + if (attach->dir != direction &&
> > >> + attach->dir != DMA_BIDIRECTIONAL)
> > >> + return ERR_PTR(-EBUSY);
> > >> +
> > >> + return attach->sgt;
> > >> + }
> > >> +
> > >> sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> > >> if (!sg_table)
> > >> sg_table = ERR_PTR(-ENOMEM);
> > >>
> > >> + if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
> > >> + attach->sgt = sg_table;
> > >> + attach->dir = direction;
> > >> + }
> > >> +
> > >> return sg_table;
> > >> }
> > >> EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
> > >> @@ -657,8 +678,10 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
> > >> if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
> > >> return;
> > >>
> > >> - attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
> > >> - direction);
> > >> + if (attach->sgt == sg_table)
> > >> + return;
> > >> +
> > >> + attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
> > >> }
> > >> EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
> > >>
> > >> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> > >> index 58725f890b5b..45b9767e67ec 100644
> > >> --- a/include/linux/dma-buf.h
> > >> +++ b/include/linux/dma-buf.h
> > >> @@ -51,6 +51,15 @@ struct dma_buf_attachment;
> > >> * @vunmap: [optional] unmaps a vmap from the buffer
> > >> */
> > >> struct dma_buf_ops {
> > >> + /**
> > >> + * @cache_sgt_mapping:
> > >> + *
> > >> + * If true the framework will cache the first mapping made for each
> > >> + * attachment. This avoids creating mappings for attachments multiple
> > >> + * times.
> > >> + */
> > >> + bool cache_sgt_mapping;
> > >> +
> > >> /**
> > >> * @attach:
> > >> *
> > >> @@ -307,6 +316,8 @@ struct dma_buf {
> > >> * @dmabuf: buffer for this attachment.
> > >> * @dev: device attached to the buffer.
> > >> * @node: list of dma_buf_attachment.
> > >> + * @sgt: cached mapping.
> > >> + * @dir: direction of cached mapping.
> > >> * @priv: exporter specific attachment data.
> > >> *
> > >> * This structure holds the attachment information between the dma_buf buffer
> > >> @@ -322,6 +333,8 @@ struct dma_buf_attachment {
> > >> struct dma_buf *dmabuf;
> > >> struct device *dev;
> > >> struct list_head node;
> > >> + struct sg_table *sgt;
> > >> + enum dma_data_direction dir;
> > >> void *priv;
> > >> };
> > >>
> > >> --
> > >> 2.17.1
> > >>
> >
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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