[Spice-devel] [PATCH 10/12] qxl-wddm-dod: Optimize allocation of memory chunks

[Yuri Benditovich]

On Tue, Mar 28, 2017 at 4:23 PM, Frediano Ziglio <fziglio at redhat.com> wrote:

> >
> > Increased size of allocation to reduce number of allocation per
> > bitmap. Before change the procedure ignored 'alloc_size' parameter
> > and always allocated memory chunk according to 'size' parameter.
> > As a result, first chunk could be up to 64K and all following are
> > limited by line size. For example, for bitmap 1280x1024 there was
> > more than 1008 chunks allocated, for bitmap 128x1024 - 897 chunks.
> > We change the procedure to use chunk size up to 64K (similar to first
> > chunk). This reduces in described examples number of allocation from
> > 1008 to 64 and 897 to 8 respectively.
> >
> > Signed-off-by: Yuri Benditovich <yuri.benditovich at daynix.com>
> > ---
> >  qxldod/QxlDod.cpp | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/qxldod/QxlDod.cpp b/qxldod/QxlDod.cpp
> > index 56a4cf2..94426dd 100755
> > --- a/qxldod/QxlDod.cpp
> > +++ b/qxldod/QxlDod.cpp
> > @@ -4586,7 +4586,7 @@ BOOLEAN QxlDevice::PutBytesAlign(QXLDataChunk
> > **chunk_ptr, UINT8 **now_ptr,
> >      UINT8 *now = *now_ptr;
> >      UINT8 *end = *end_ptr;
> >      size_t maxAllocSize = BITS_BUF_MAX - BITS_BUF_MAX % size;
> > -    alloc_size = MIN(size, maxAllocSize);
> > +    alloc_size = MIN(alloc_size, maxAllocSize);
> >      DbgPrint(TRACE_LEVEL_VERBOSE, ("---> %s\n", __FUNCTION__));
> >
> >      while (size) {
>
> As far as I can see this fix a regression introduced in 9/12 so
> should be squashed together with 9/12.
>

There was no regression in 9/12, see commit description
This patch forces the driver to make bigger allocations and in result we
will have smaller amount of allocations per operation.



>
> On the same subject. Why we need to split the allocations?
> Can't we try to allocate the whole image in one chunk and
> only if fails fall back to multiple chunks ?
>

No, we can't do that, as maximal size of allocation from device memory in
driver's code was always limited by ~64K.
So allocation were always splitted, see numbers in commit description.
I suppose there is some reason for that.


> Frediano
>
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