diff options
Diffstat (limited to 'src/threading_strategy.cc')
| -rw-r--r-- | src/threading_strategy.cc | 25 |
1 files changed, 13 insertions, 12 deletions
diff --git a/src/threading_strategy.cc b/src/threading_strategy.cc index cd4d576..17ce18f 100644 --- a/src/threading_strategy.cc +++ b/src/threading_strategy.cc @@ -36,24 +36,25 @@ constexpr int kFrameParallelThresholdMultiplier = // Computes the number of frame threads to be used based on the following // heuristic: // * If |thread_count| == 1, return 0. -// * If |thread_count| <= |tile_count| * 4, return 0. +// * If |thread_count| <= |tile_count| * kFrameParallelThresholdMultiplier, +// return 0. // * Otherwise, return the largest value of i which satisfies the following // condition: i + i * tile_columns <= thread_count. This ensures that there // are at least |tile_columns| worker threads for each frame thread. // * This function will never return 1 or a value > |thread_count|. // -// This heuristic is based empirical performance data. The in-frame threading -// model (combination of tile multithreading, superblock row multithreading and -// post filter multithreading) performs better than the frame parallel model -// until we reach the threshold of |thread_count| > |tile_count| * -// kFrameParallelThresholdMultiplier. +// This heuristic is based on empirical performance data. The in-frame +// threading model (combination of tile multithreading, superblock row +// multithreading and post filter multithreading) performs better than the +// frame parallel model until we reach the threshold of |thread_count| > +// |tile_count| * kFrameParallelThresholdMultiplier. // // It is a function of |tile_count| since tile threading and superblock row -// multithreading will scale only as a factor of |tile_count|. The threshold 4 -// is arrived at based on empirical data. The general idea is that superblock -// row multithreading plateaus at 4 * |tile_count| because in most practical -// cases there aren't more than that many superblock rows and columns available -// to work on in parallel. +// multithreading will scale only as a factor of |tile_count|. The threshold +// kFrameParallelThresholdMultiplier is arrived at based on empirical data. +// The general idea is that superblock row multithreading plateaus at 4 * +// |tile_count| because in most practical cases there aren't more than that +// many superblock rows and columns available to work on in parallel. int ComputeFrameThreadCount(int thread_count, int tile_count, int tile_columns) { assert(thread_count > 0); @@ -132,7 +133,7 @@ bool ThreadingStrategy::Reset(const ObuFrameHeader& frame_header, thread_count -= 2; if (thread_count <= 0) break; } -#else // !defined(__ANDROID__) +#else // !defined(__ANDROID__) // Assign the remaining threads to each Tile. for (int i = 0; i < tile_count; ++i) { const int count = thread_count / tile_count + |