[OpenJDK 2D-Dev] [9] request for review: 8087201: OGL: rendering of lcd text is slow

[Andrew Brygin]

Hello Sergey,

  the only part of the fix affects the performance of AA case: the cache 
cell size.
  In a case of retina, 13pt and 20pt glyphs do not fit the 16x16 cache 
cells,
  so these benchmarks show better performance:
  13pt: 40-80 times faster
  20pt: 7-13 times faster

  6pt shows the same results, because it fits the cache in any case.

  Full benchmark results:
  http://cr.openjdk.java.net/~bae/8087201/9/ogl-lcd-aa.res

  Regarding the suggestion with creating a separate method for the fast
  path possibility check: please note that we do this check and calculate
  the dstTextureID only once per whole glyph vector, but use the 
dstTextureID
  as an indicator for every glyph. So such change will affect 
performance for
  sure.
  Probably we can masquerade  the 'dstTextureID == 0' condition with some
  sort of a macro, like canReadDestinationDirectly() or something like this.
  Are you OK with this?

Thanks,
Andrew

19/06/15 13:57, Sergey Bylokhov wrote:
> Hi, Andrew.
> Can you additionally provide the bench data about aa(before/after the 
> fix) vs new lcd lcd?
>
> Probably it well be more obvious if the code in OGLTextRenderer
> 1007     if (OGLC_IS_CAP_PRESENT(oglc, CAPS_EXT_TEXBARRIER) &&
> 1008         dstOps->textureTarget == GL_TEXTURE_2D)
>
> Will be moved to the separate method and the check to the possibility 
> of fast blit will be clarified instead of:
> if (dstTextureID == 0) {
>
> Also your review request contains useful information like 
> fast/slow/read-after-write etc. I think this information can be useful 
> as a comments in the code.
>
> On 18.06.15 17:39, Andrew Brygin wrote:
>> Hello,
>>
>>  could you please review a fix for 8087201?
>>
>>  The root of the problem is that we have to supply a content of
>>  destination surface to lcd shader to compose the lcd glyph correctly.
>>  In order to do this, we have to copy a sub-image from destination
>>  buffer to an intermediate texture using glCopyTexSubImage2D() routine.
>>  Unfortunately, this routine is quite slow on majority of systems, 
>> and it
>>  dramatically reduces the overall speed of lcd text rendering.
>>
>>  The main idea of the fix is to use a texture associated with the 
>> destination
>>  surface if it exists. In this case we have a chance to completely 
>> abandon the
>>  data copying. However, we have to avoid read-after-write in order to 
>> get
>>  correct results in this case. Fortunately, it can be achieved by 
>> using the
>>  GL_NV_texture_barrier extension:
>>
>> https://www.opengl.org/registry/specs/NV/texture_barrier.txt
>>
>> Beside this, suggested fix introduces following changes in OGL text 
>> renderer:
>>
>> * Separate accelerated caches for LCD and AA glyphs
>>    We have a single cache which is initialized ether for LCD or for 
>> AA glyphs.
>>    If application mixes these types of font smoothing from some 
>> reasons, we
>>    have got a significant performance degradation.
>>    For example, if we use J2DBench in GUI mode, then swing GUI 
>> initializes the
>>    accelerated cache for AA,  and subsequent rendering of LCD text 
>> always
>>    uses 'no-cache' code path.
>>
>> * Increase dimension of the glyph cache cell from 16x16 to 32x32.
>>    This change gives significant performance boost on systems with 
>> retina
>>   (because of average size of rendered glyphs).
>>    However, on systems where the fast path with destination texture 
>> is not
>>    possible for any reasons, this change may cause a performance 
>> degradation
>>    because of more extenceive usage of glCopyTexSubImage2D.
>>   So, we probably may want to get a means to configure the cell 
>> dimension
>>   depending on system capabilities.
>>
>> Performance results overview:
>> * MBP with Intel Iris (retina, texture barrier is available):
>>   http://cr.openjdk.java.net/~bae/8087201/9/mbp-intel-iris.txt
>>
>> * iMac with AMD HD6750M (no retina, texture barrier is available):
>>   http://cr.openjdk.java.net/~bae/8087201/9/imac-amd-hd6750m.txt
>>
>> * MBP with OSX10.8, NV GF9600M (no retina, no texture barrier):
>> http://cr.openjdk.java.net/~bae/8087201/9/mbp-10.8-NVGF9600M.txt
>>
>> Please take a look.
>>
>> Thanks,
>> Andrew
>
>