From c6ede090350c9f413b1df8a4de850da5345797e2 Mon Sep 17 00:00:00 2001 From: JosJuice Date: Sun, 27 Jun 2021 17:24:53 +0200 Subject: [PATCH] DVDInterface: Don't evict cache block i unless block i + 2 was read Intends to fix https://bugs.dolphin-emu.org/issues/12279. I have hardware tested the behavior, but I haven't tested the game. --- Source/Core/Core/HW/DVD/DVDInterface.cpp | 29 ++++++++++++++++-------- 1 file changed, 20 insertions(+), 9 deletions(-) diff --git a/Source/Core/Core/HW/DVD/DVDInterface.cpp b/Source/Core/Core/HW/DVD/DVDInterface.cpp index dd9a2c0ccf..018492319e 100644 --- a/Source/Core/Core/HW/DVD/DVDInterface.cpp +++ b/Source/Core/Core/HW/DVD/DVDInterface.cpp @@ -1512,27 +1512,38 @@ static void ScheduleReads(u64 offset, u32 length, const DiscIO::Partition& parti dvd_offset += DVD_ECC_BLOCK_SIZE; } while (length > 0); - // Update the buffer based on this read. Based on experimental testing, - // we will only reuse the old buffer while reading forward. Note that the - // buffer start we calculate here is not the actual start of the buffer - - // it is just the start of the portion we need to read. + // Evict blocks from the buffer which are unlikely to be used again after this read, + // so that the buffer gets space for prefetching new blocks. Based on hardware testing, + // the blocks which are kept are the most recently accessed block, the block immediately + // before it, and all blocks after it. + // + // If the block immediately before the most recently accessed block is not kept, loading + // screens in Pitfall: The Lost Expedition are longer than they should be. + // https://bugs.dolphin-emu.org/issues/12279 const u64 last_block = dvd_offset; - if (last_block == buffer_start + DVD_ECC_BLOCK_SIZE && buffer_start != buffer_end) + constexpr u32 BUFFER_BACKWARD_SEEK_LIMIT = DVD_ECC_BLOCK_SIZE * 2; + if (last_block - buffer_start <= BUFFER_BACKWARD_SEEK_LIMIT && buffer_start != buffer_end) { - // Special case: reading less than one block at the start of the - // buffer won't change the buffer state + // Special case: reading the first two blocks of the buffer doesn't change the buffer state } else { + // Note that the s_read_buffer_start_offset value we calculate here is not the + // actual start of the buffer - it is just the start of the portion we need to read. + // The actual start of the buffer is s_read_buffer_end_offset - STREAMING_BUFFER_SIZE. if (last_block >= buffer_end) + { // Full buffer read s_read_buffer_start_offset = last_block; + } else + { // Partial buffer read s_read_buffer_start_offset = buffer_end; + } - s_read_buffer_end_offset = last_block + STREAMING_BUFFER_SIZE - DVD_ECC_BLOCK_SIZE; - // Assume the buffer starts reading right after the end of the last operation + s_read_buffer_end_offset = last_block + STREAMING_BUFFER_SIZE - BUFFER_BACKWARD_SEEK_LIMIT; + // Assume the buffer starts prefetching new blocks right after the end of the last operation s_read_buffer_start_time = current_time + ticks_until_completion; s_read_buffer_end_time = s_read_buffer_start_time +