shared_memory_abi: Remove unused function and update comment
The fragment size is not necessarily 4 bytes long since
6e516e800c31("protozero: Pack length fields for short nested messages"):
old implementations of tracing service do not seem to have a problem
with this.
Bug: 162206162
Change-Id: If1ebb22d3f1ef553af58933c8944063ccb9f02cf
diff --git a/include/perfetto/ext/tracing/core/shared_memory_abi.h b/include/perfetto/ext/tracing/core/shared_memory_abi.h
index 4e05599..dd146ea 100644
--- a/include/perfetto/ext/tracing/core/shared_memory_abi.h
+++ b/include/perfetto/ext/tracing/core/shared_memory_abi.h
@@ -153,8 +153,10 @@
// See PageLayout below.
static constexpr size_t kMaxChunksPerPage = 14;
- // Each TracePacket in the Chunk is prefixed by a 4 bytes redundant VarInt
- // (see proto_utils.h) stating its size.
+ // Each TracePacket fragment in the Chunk is prefixed by a VarInt stating its
+ // size that is up to 4 bytes long. Since the size is often known after the
+ // fragment has been filled, the VarInt is often redundantly encoded (see
+ // proto_utils.h) to be exactly 4 bytes.
static constexpr size_t kPacketHeaderSize = 4;
// TraceWriter specifies this invalid packet/fragment size to signal to the
@@ -416,19 +418,6 @@
return packets.count;
}
- // Increases |packets.count| to the given |packet_count|, but only if
- // |packet_count| is larger than the current value of |packets.count|.
- // Returns the new packet count. Same atomicity guarantees as
- // IncrementPacketCount().
- uint16_t IncreasePacketCountTo(uint16_t packet_count) {
- ChunkHeader* chunk_header = header();
- auto packets = chunk_header->packets.load(std::memory_order_relaxed);
- if (packets.count < packet_count)
- packets.count = packet_count & ChunkHeader::Packets::kMaxCount;
- chunk_header->packets.store(packets, std::memory_order_release);
- return packets.count;
- }
-
// Flags are cleared by TryAcquireChunk(), by passing the new header for
// the chunk, or through ClearNeedsPatchingFlag.
void SetFlag(ChunkHeader::Flags flag) {
