Use compress and decompress slice_buffers only when they are needed.

Compression is not used for performance senstiive RPCs, yet
chttp2 always moves buffers in/out of the compressed/decmpressed
buffers. Even initilizing them is costly.

Use the (de)compression buffer and state only when we are using
non-identity compression.

This is part of a larger performance change, and this one buys us 1%-2%
depending on the benchmark.

src/core/ext/transport/chttp2/transport/chttp2_transport.cc

@@ -679,8 +679,6 @@ grpc_chttp2_stream::grpc_chttp2_stream(grpc_chttp2_transport* t,
   grpc_slice_buffer_init(&frame_storage);
   grpc_slice_buffer_init(&unprocessed_incoming_frames_buffer);
   grpc_slice_buffer_init(&flow_controlled_buffer);
-  grpc_slice_buffer_init(&compressed_data_buffer);
-  grpc_slice_buffer_init(&decompressed_data_buffer);
 
   GRPC_CLOSURE_INIT(&complete_fetch_locked, ::complete_fetch_locked, this,
                     grpc_combiner_scheduler(t->combiner));
@@ -704,8 +702,13 @@ grpc_chttp2_stream::~grpc_chttp2_stream() {
 
   grpc_slice_buffer_destroy_internal(&unprocessed_incoming_frames_buffer);
   grpc_slice_buffer_destroy_internal(&frame_storage);
-  grpc_slice_buffer_destroy_internal(&compressed_data_buffer);
-  grpc_slice_buffer_destroy_internal(&decompressed_data_buffer);
+  if (stream_compression_method != GRPC_STREAM_COMPRESSION_IDENTITY_COMPRESS) {
+    grpc_slice_buffer_destroy_internal(&compressed_data_buffer);
+  }
+  if (stream_decompression_method !=
+      GRPC_STREAM_COMPRESSION_IDENTITY_DECOMPRESS) {
+    grpc_slice_buffer_destroy_internal(&decompressed_data_buffer);
+  }
 
   grpc_chttp2_list_remove_stalled_by_transport(t, this);
   grpc_chttp2_list_remove_stalled_by_stream(t, this);
@@ -759,12 +762,15 @@ static void destroy_stream(grpc_transport* gt, grpc_stream* gs,
   GPR_TIMER_SCOPE("destroy_stream", 0);
   grpc_chttp2_transport* t = reinterpret_cast<grpc_chttp2_transport*>(gt);
   grpc_chttp2_stream* s = reinterpret_cast<grpc_chttp2_stream*>(gs);
-
-  if (s->stream_compression_ctx != nullptr) {
+  if (s->stream_compression_method !=
+          GRPC_STREAM_COMPRESSION_IDENTITY_COMPRESS &&
+      s->stream_compression_ctx != nullptr) {
     grpc_stream_compression_context_destroy(s->stream_compression_ctx);
     s->stream_compression_ctx = nullptr;
   }
-  if (s->stream_decompression_ctx != nullptr) {
+  if (s->stream_decompression_method !=
+          GRPC_STREAM_COMPRESSION_IDENTITY_DECOMPRESS &&
+      s->stream_decompression_ctx != nullptr) {
     grpc_stream_compression_context_destroy(s->stream_decompression_ctx);
     s->stream_decompression_ctx = nullptr;
   }
@@ -1443,6 +1449,13 @@ static void perform_stream_op_locked(void* stream_op,
       s->stream_compression_method = GRPC_STREAM_COMPRESSION_IDENTITY_COMPRESS;
     }
 
+    if (s->stream_compression_method !=
+        GRPC_STREAM_COMPRESSION_IDENTITY_COMPRESS) {
+      s->uncompressed_data_size = 0;
+      s->stream_compression_ctx = nullptr;
+      grpc_slice_buffer_init(&s->compressed_data_buffer);
+    }
+
     s->send_initial_metadata_finished = add_closure_barrier(on_complete);
     s->send_initial_metadata =
         op_payload->send_initial_metadata.send_initial_metadata;
@@ -1998,27 +2011,39 @@ void grpc_chttp2_maybe_complete_recv_trailing_metadata(grpc_chttp2_transport* t,
         !s->seen_error && s->recv_trailing_metadata_finished != nullptr) {
       /* Maybe some SYNC_FLUSH data is left in frame_storage. Consume them and
        * maybe decompress the next 5 bytes in the stream. */
-      bool end_of_context;
-      if (!s->stream_decompression_ctx) {
-        s->stream_decompression_ctx = grpc_stream_compression_context_create(
-            s->stream_decompression_method);
-      }
-      if (!grpc_stream_decompress(
-              s->stream_decompression_ctx, &s->frame_storage,
-              &s->unprocessed_incoming_frames_buffer, nullptr,
-              GRPC_HEADER_SIZE_IN_BYTES, &end_of_context)) {
-        grpc_slice_buffer_reset_and_unref_internal(&s->frame_storage);
-        grpc_slice_buffer_reset_and_unref_internal(
-            &s->unprocessed_incoming_frames_buffer);
-        s->seen_error = true;
-      } else {
+      if (s->stream_decompression_method ==
+          GRPC_STREAM_COMPRESSION_IDENTITY_DECOMPRESS) {
+        grpc_slice_buffer_move_first(&s->frame_storage,
+                                     GRPC_HEADER_SIZE_IN_BYTES,
+                                     &s->unprocessed_incoming_frames_buffer);
         if (s->unprocessed_incoming_frames_buffer.length > 0) {
           s->unprocessed_incoming_frames_decompressed = true;
           pending_data = true;
         }
-        if (end_of_context) {
-          grpc_stream_compression_context_destroy(s->stream_decompression_ctx);
-          s->stream_decompression_ctx = nullptr;
+      } else {
+        bool end_of_context;
+        if (!s->stream_decompression_ctx) {
+          s->stream_decompression_ctx = grpc_stream_compression_context_create(
+              s->stream_decompression_method);
+        }
+        if (!grpc_stream_decompress(
+                s->stream_decompression_ctx, &s->frame_storage,
+                &s->unprocessed_incoming_frames_buffer, nullptr,
+                GRPC_HEADER_SIZE_IN_BYTES, &end_of_context)) {
+          grpc_slice_buffer_reset_and_unref_internal(&s->frame_storage);
+          grpc_slice_buffer_reset_and_unref_internal(
+              &s->unprocessed_incoming_frames_buffer);
+          s->seen_error = true;
+        } else {
+          if (s->unprocessed_incoming_frames_buffer.length > 0) {
+            s->unprocessed_incoming_frames_decompressed = true;
+            pending_data = true;
+          }
+          if (end_of_context) {
+            grpc_stream_compression_context_destroy(
+                s->stream_decompression_ctx);
+            s->stream_decompression_ctx = nullptr;
+          }
         }
       }
     }
@@ -2941,6 +2966,8 @@ bool Chttp2IncomingByteStream::Next(size_t max_size_hint,
 }
 
 void Chttp2IncomingByteStream::MaybeCreateStreamDecompressionCtx() {
+  GPR_DEBUG_ASSERT(stream_->stream_decompression_method !=
+                   GRPC_STREAM_COMPRESSION_IDENTITY_DECOMPRESS);
   if (!stream_->stream_decompression_ctx) {
     stream_->stream_decompression_ctx = grpc_stream_compression_context_create(
         stream_->stream_decompression_method);
@@ -2951,7 +2978,9 @@ grpc_error* Chttp2IncomingByteStream::Pull(grpc_slice* slice) {
   GPR_TIMER_SCOPE("incoming_byte_stream_pull", 0);
   grpc_error* error;
   if (stream_->unprocessed_incoming_frames_buffer.length > 0) {
-    if (!stream_->unprocessed_incoming_frames_decompressed) {
+    if (!stream_->unprocessed_incoming_frames_decompressed &&
+        stream_->stream_decompression_method !=
+            GRPC_STREAM_COMPRESSION_IDENTITY_DECOMPRESS) {
       bool end_of_context;
       MaybeCreateStreamDecompressionCtx();
       if (!grpc_stream_decompress(stream_->stream_decompression_ctx,

src/core/ext/transport/chttp2/transport/hpack_parser.cc

@@ -1616,6 +1616,12 @@ static void parse_stream_compression_md(grpc_chttp2_transport* t,
     s->stream_decompression_method =
         GRPC_STREAM_COMPRESSION_IDENTITY_DECOMPRESS;
   }
+
+  if (s->stream_decompression_method !=
+      GRPC_STREAM_COMPRESSION_IDENTITY_DECOMPRESS) {
+    s->stream_decompression_ctx = nullptr;
+    grpc_slice_buffer_init(&s->decompressed_data_buffer);
+  }
 }
 
 grpc_error* grpc_chttp2_header_parser_parse(void* hpack_parser,

src/core/ext/transport/chttp2/transport/internal.h

@@ -583,10 +583,6 @@ struct grpc_chttp2_stream {
 
   grpc_slice_buffer frame_storage; /* protected by t combiner */
 
-  /* Accessed only by transport thread when stream->pending_byte_stream == false
-   * Accessed only by application thread when stream->pending_byte_stream ==
-   * true */
-  grpc_slice_buffer unprocessed_incoming_frames_buffer;
   grpc_closure* on_next = nullptr;  /* protected by t combiner */
   bool pending_byte_stream = false; /* protected by t combiner */
   // cached length of buffer to be used by the transport thread in cases where
@@ -594,6 +590,10 @@ struct grpc_chttp2_stream {
   // application threads are allowed to modify
   // unprocessed_incoming_frames_buffer
   size_t unprocessed_incoming_frames_buffer_cached_length = 0;
+  /* Accessed only by transport thread when stream->pending_byte_stream == false
+   * Accessed only by application thread when stream->pending_byte_stream ==
+   * true */
+  grpc_slice_buffer unprocessed_incoming_frames_buffer;
   grpc_closure reset_byte_stream;
   grpc_error* byte_stream_error = GRPC_ERROR_NONE; /* protected by t combiner */
   bool received_last_frame = false;                /* protected by t combiner */
@@ -634,18 +634,7 @@ struct grpc_chttp2_stream {
   /* Stream decompression method to be used. */
   grpc_stream_compression_method stream_decompression_method =
       GRPC_STREAM_COMPRESSION_IDENTITY_DECOMPRESS;
-  /** Stream compression decompress context */
-  grpc_stream_compression_context* stream_decompression_ctx = nullptr;
-  /** Stream compression compress context */
-  grpc_stream_compression_context* stream_compression_ctx = nullptr;
 
-  /** Buffer storing data that is compressed but not sent */
-  grpc_slice_buffer compressed_data_buffer;
-  /** Amount of uncompressed bytes sent out when compressed_data_buffer is
-   * emptied */
-  size_t uncompressed_data_size = 0;
-  /** Temporary buffer storing decompressed data */
-  grpc_slice_buffer decompressed_data_buffer;
   /** Whether bytes stored in unprocessed_incoming_byte_stream is decompressed
    */
   bool unprocessed_incoming_frames_decompressed = false;
@@ -655,6 +644,22 @@ struct grpc_chttp2_stream {
   size_t decompressed_header_bytes = 0;
   /** Byte counter for number of bytes written */
   size_t byte_counter = 0;
+
+  /** Amount of uncompressed bytes sent out when compressed_data_buffer is
+   * emptied */
+  size_t uncompressed_data_size;
+  /** Stream compression compress context */
+  grpc_stream_compression_context* stream_compression_ctx;
+  /** Buffer storing data that is compressed but not sent */
+  grpc_slice_buffer compressed_data_buffer;
+
+  /** Stream compression decompress context */
+  grpc_stream_compression_context* stream_decompression_ctx;
+  /** Temporary buffer storing decompressed data.
+   * Initialized, used, and destroyed only when stream uses (non-identity)
+   * compression.
+   */
+  grpc_slice_buffer decompressed_data_buffer;
 };
 
 /** Transport writing call flow:

src/core/ext/transport/chttp2/transport/writing.cc

@@ -25,6 +25,7 @@
 
 #include <grpc/support/log.h>
 
+#include "src/core/lib/compression/stream_compression.h"
 #include "src/core/lib/debug/stats.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/slice/slice_internal.h"
@@ -150,7 +151,11 @@ static void report_stall(grpc_chttp2_transport* t, grpc_chttp2_stream* s,
         ":flowed=%" PRId64 ":peer_initwin=%d:t_win=%" PRId64
         ":s_win=%d:s_delta=%" PRId64 "]",
         t->peer_string, t, s->id, staller, s->flow_controlled_buffer.length,
-        s->compressed_data_buffer.length, s->flow_controlled_bytes_flowed,
+        s->stream_compression_method ==
+                GRPC_STREAM_COMPRESSION_IDENTITY_COMPRESS
+            ? 0
+            : s->compressed_data_buffer.length,
+        s->flow_controlled_bytes_flowed,
         t->settings[GRPC_ACKED_SETTINGS]
                    [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE],
         t->flow_control->remote_window(),
@@ -325,7 +330,23 @@ class DataSendContext {
 
   bool AnyOutgoing() const { return max_outgoing() > 0; }
 
+  void FlushUncompressedBytes() {
+    uint32_t send_bytes = static_cast<uint32_t> GPR_MIN(
+        max_outgoing(), s_->flow_controlled_buffer.length);
+    is_last_frame_ = send_bytes == s_->flow_controlled_buffer.length &&
+                     s_->fetching_send_message == nullptr &&
+                     s_->send_trailing_metadata != nullptr &&
+                     grpc_metadata_batch_is_empty(s_->send_trailing_metadata);
+    grpc_chttp2_encode_data(s_->id, &s_->flow_controlled_buffer, send_bytes,
+                            is_last_frame_, &s_->stats.outgoing, &t_->outbuf);
+    s_->flow_control->SentData(send_bytes);
+    s_->sending_bytes += send_bytes;
+  }
+
   void FlushCompressedBytes() {
+    GPR_DEBUG_ASSERT(s_->stream_compression_method !=
+                     GRPC_STREAM_COMPRESSION_IDENTITY_COMPRESS);
+
     uint32_t send_bytes = static_cast<uint32_t> GPR_MIN(
         max_outgoing(), s_->compressed_data_buffer.length);
     bool is_last_data_frame =
@@ -360,6 +381,9 @@ class DataSendContext {
   }
 
   void CompressMoreBytes() {
+    GPR_DEBUG_ASSERT(s_->stream_compression_method !=
+                     GRPC_STREAM_COMPRESSION_IDENTITY_COMPRESS);
+
     if (s_->stream_compression_ctx == nullptr) {
       s_->stream_compression_ctx =
           grpc_stream_compression_context_create(s_->stream_compression_method);
@@ -417,7 +441,7 @@ class StreamWriteContext {
     // https://github.com/grpc/proposal/blob/master/A6-client-retries.md#when-retries-are-valid
     if (!t_->is_client && s_->fetching_send_message == nullptr &&
         s_->flow_controlled_buffer.length == 0 &&
-        s_->compressed_data_buffer.length == 0 &&
+        compressed_data_buffer_len() == 0 &&
         s_->send_trailing_metadata != nullptr &&
         is_default_initial_metadata(s_->send_initial_metadata)) {
       ConvertInitialMetadataToTrailingMetadata();
@@ -446,6 +470,13 @@ class StreamWriteContext {
         "send_initial_metadata_finished");
   }
 
+  bool compressed_data_buffer_len() {
+    return s_->stream_compression_method ==
+                   GRPC_STREAM_COMPRESSION_IDENTITY_COMPRESS
+               ? 0
+               : s_->compressed_data_buffer.length;
+  }
+
   void FlushWindowUpdates() {
     /* send any window updates */
     const uint32_t stream_announce = s_->flow_control->MaybeSendUpdate();
@@ -462,7 +493,7 @@ class StreamWriteContext {
     if (!s_->sent_initial_metadata) return;
 
     if (s_->flow_controlled_buffer.length == 0 &&
-        s_->compressed_data_buffer.length == 0) {
+        compressed_data_buffer_len() == 0) {
       return;  // early out: nothing to do
     }
 
@@ -479,13 +510,21 @@ class StreamWriteContext {
       return;  // early out: nothing to do
     }
 
-    while ((s_->flow_controlled_buffer.length > 0 ||
-            s_->compressed_data_buffer.length > 0) &&
-           data_send_context.max_outgoing() > 0) {
-      if (s_->compressed_data_buffer.length > 0) {
-        data_send_context.FlushCompressedBytes();
-      } else {
-        data_send_context.CompressMoreBytes();
+    if (s_->stream_compression_method ==
+        GRPC_STREAM_COMPRESSION_IDENTITY_COMPRESS) {
+      while (s_->flow_controlled_buffer.length > 0 &&
+             data_send_context.max_outgoing() > 0) {
+        data_send_context.FlushUncompressedBytes();
+      }
+    } else {
+      while ((s_->flow_controlled_buffer.length > 0 ||
+              s_->compressed_data_buffer.length > 0) &&
+             data_send_context.max_outgoing() > 0) {
+        if (s_->compressed_data_buffer.length > 0) {
+          data_send_context.FlushCompressedBytes();
+        } else {
+          data_send_context.CompressMoreBytes();
+        }
       }
     }
     write_context_->ResetPingClock();
@@ -495,7 +534,7 @@ class StreamWriteContext {
     data_send_context.CallCallbacks();
     stream_became_writable_ = true;
     if (s_->flow_controlled_buffer.length > 0 ||
-        s_->compressed_data_buffer.length > 0) {
+        compressed_data_buffer_len() > 0) {
       GRPC_CHTTP2_STREAM_REF(s_, "chttp2_writing:fork");
       grpc_chttp2_list_add_writable_stream(t_, s_);
     }
@@ -508,7 +547,7 @@ class StreamWriteContext {
     if (s_->send_trailing_metadata == nullptr) return;
     if (s_->fetching_send_message != nullptr) return;
     if (s_->flow_controlled_buffer.length != 0) return;
-    if (s_->compressed_data_buffer.length != 0) return;
+    if (compressed_data_buffer_len() != 0) return;
 
     GRPC_CHTTP2_IF_TRACING(gpr_log(GPR_INFO, "sending trailing_metadata"));
     if (grpc_metadata_batch_is_empty(s_->send_trailing_metadata)) {