[Mesa-dev] [PATCH 2/2] pb_bufmgr_cache: add is_buffer_busy hook and use it instead of non-blocking map

[Marek Olšák]

On Mon, Feb 14, 2011 at 6:47 PM, José Fonseca <jfonseca at vmware.com> wrote:

> On Sun, 2011-02-13 at 23:58 -0800, Dave Airlie wrote:
> > >>    if(buf->base.base.size < size)
> > >>       return 0;
> > >>
> > >> @@ -242,13 +240,10 @@ pb_cache_is_buffer_compat(struct pb_cache_buffer
> > >> *buf,
> > >>    if(!pb_check_usage(desc->usage, buf->base.base.usage))
> > >>       return 0;
> > >>
> > >> -   map = pb_map(buf->buffer, PB_USAGE_DONTBLOCK, NULL);
> > >> -   if (!map) {
> > >> -      return -1;
> > >> -   }
> > >> +   if (buf->mgr->base.is_buffer_busy)
> > >> +      if (buf->mgr->base.is_buffer_busy(&buf->mgr->base,
> buf->buffer))
> > >> +         return -1;
> > >
> > > Oops, this is wrong. I will locally replace any occurences of
> > > "buf->mgr->base(.)" with "buf->mgr->provider(->)", which is how it was
> meant
> > > to be, but the idea remains the same. Please review.
>
> Marek, I don't understand what you want to do here: you removed the
> pb_map, but you left the pb_unmap, and what will happen if
> is_buffer_busy is not defined?
>

I didn't leave the pb_unmap call, it was removed too, I just cut it off in
my second email, since it wasn't relevant to the typo. Sorry about that. So
there's only one way: is_buffer_busy.


> >
> > I actually suggested this originally, but Jose I think preferred using
> > the dontblock to the buffer mapping.
>
> I'd prefer that there is one way of doing this, but I didn't/don't feel
> strong about this. IMO, having two ways, PB_USAGE_DONTBLOCK and
> is_buffer_busy, is not cleaner that just PB_USAGE_DONTBLOCK, even if
> is_buffer_busy is conceptually cleaner.
>

The thing is mapping a buffer just to know whether it's being used is
unnecessary, and the mapping itself may be slower than a simple is_busy
query.


> Marek, Would adding an inline function, pb_is_buffer_busy, that calls
> pb_map(PB_USAGE_DONTBLOCK)+pb_unmap inside work for you?
>
> Another way, would be to add is_buffer_busy and have the default
> implementation to do pb_map/pb_unmap.
>

I can add a piece of code that uses pb_map/pb_unmap if the is_buffer_busy
hook is not set, so that the original behavior is preserved. Would that be
ok with you? Here's a new patch:


    pb_bufmgr_cache: add is_buffer_busy hook and use it instead of
non-blocking map

    This is cleaner and implementing the hook is optional.

diff --git a/src/gallium/auxiliary/pipebuffer/pb_bufmgr.h
b/src/gallium/auxiliary/pipebuffer/pb_bufm
index 2ef0216..960068c 100644
--- a/src/gallium/auxiliary/pipebuffer/pb_bufmgr.h
+++ b/src/gallium/auxiliary/pipebuffer/pb_bufmgr.h
@@ -82,6 +82,10 @@ struct pb_manager
     */
    void
    (*flush)( struct pb_manager *mgr );
+
+   boolean
+   (*is_buffer_busy)( struct pb_manager *mgr,
+                      struct pb_buffer *buf );
 };


diff --git a/src/gallium/auxiliary/pipebuffer/pb_bufmgr_cache.c
b/src/gallium/auxiliary/pipebuffer/p
index a6eb403..25accef 100644
--- a/src/gallium/auxiliary/pipebuffer/pb_bufmgr_cache.c
+++ b/src/gallium/auxiliary/pipebuffer/pb_bufmgr_cache.c
@@ -227,8 +227,6 @@ pb_cache_is_buffer_compat(struct pb_cache_buffer *buf,
                           pb_size size,
                           const struct pb_desc *desc)
 {
-   void *map;
-
    if(buf->base.base.size < size)
       return 0;

@@ -242,13 +240,18 @@ pb_cache_is_buffer_compat(struct pb_cache_buffer *buf,
    if(!pb_check_usage(desc->usage, buf->base.base.usage))
       return 0;

-   map = pb_map(buf->buffer, PB_USAGE_DONTBLOCK, NULL);
-   if (!map) {
-      return -1;
+   if (buf->mgr->provider->is_buffer_busy) {
+      if (buf->mgr->provider->is_buffer_busy(buf->mgr->provider,
buf->buffer))
+         return -1;
+   } else {
+      void *ptr = pb_map(buf->buffer, PB_USAGE_DONTBLOCK, NULL);
+
+      if (!ptr)
+         return -1;
+
+      pb_unmap(buf->buffer);
    }

-   pb_unmap(buf->buffer);
-
    return 1;
 }

Marek
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