Allow application optimization targets to be hinted to grpc (prefer latency over throughput for now)

include/grpc/impl/codegen/grpc_types.h

@@ -287,6 +287,14 @@ typedef struct {
 /** If non-zero, grpc server's cronet compression workaround will be enabled */
 #define GRPC_ARG_WORKAROUND_CRONET_COMPRESSION \
   "grpc.workaround.cronet_compression"
+/** String defining the optimization target for a channel.
+    Can be: "latency"    - attempt to minimize latency at the cost of throughput
+            "blend"      - try to balance latency and throughput
+            "throughput" - attempt to maximize throughput at the expense of
+                           latency
+    Defaults to "blend". In the current implementation "blend" is equivalent to
+    "latency". */
+#define GRPC_ARG_OPTIMIZATION_TARGET "grpc.optimization_target"
 /** \} */
 
 /** Result of a grpc call. If the caller satisfies the prerequisites of a

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

@@ -34,6 +34,7 @@
 #include "src/core/ext/transport/chttp2/transport/varint.h"
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/http/parser.h"
+#include "src/core/lib/iomgr/executor.h"
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/slice/slice_internal.h"
@@ -269,8 +270,6 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   grpc_slice_buffer_init(&t->outbuf);
   grpc_chttp2_hpack_compressor_init(&t->hpack_compressor);
 
-  GRPC_CLOSURE_INIT(&t->write_action, write_action, t,
-                    grpc_schedule_on_exec_ctx);
   GRPC_CLOSURE_INIT(&t->read_action_locked, read_action_locked, t,
                     grpc_combiner_scheduler(t->combiner));
   GRPC_CLOSURE_INIT(&t->benign_reclaimer_locked, benign_reclaimer_locked, t,
@@ -387,6 +386,8 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   }
   t->keepalive_permit_without_calls = g_default_keepalive_permit_without_calls;
 
+  t->opt_target = GRPC_CHTTP2_OPTIMIZE_FOR_LATENCY;
+
   if (channel_args) {
     for (i = 0; i < channel_args->num_args; i++) {
       if (0 == strcmp(channel_args->args[i].key,
@@ -475,6 +476,23 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
         t->keepalive_permit_without_calls =
             (uint32_t)grpc_channel_arg_get_integer(
                 &channel_args->args[i], (grpc_integer_options){0, 0, 1});
+      } else if (0 == strcmp(channel_args->args[i].key,
+                             GRPC_ARG_OPTIMIZATION_TARGET)) {
+        if (channel_args->args[i].type != GRPC_ARG_STRING) {
+          gpr_log(GPR_ERROR, "%s should be a string",
+                  GRPC_ARG_OPTIMIZATION_TARGET);
+        } else if (0 == strcmp(channel_args->args[i].value.string, "blend")) {
+          t->opt_target = GRPC_CHTTP2_OPTIMIZE_FOR_LATENCY;
+        } else if (0 == strcmp(channel_args->args[i].value.string, "latency")) {
+          t->opt_target = GRPC_CHTTP2_OPTIMIZE_FOR_LATENCY;
+        } else if (0 ==
+                   strcmp(channel_args->args[i].value.string, "throughput")) {
+          t->opt_target = GRPC_CHTTP2_OPTIMIZE_FOR_THROUGHPUT;
+        } else {
+          gpr_log(GPR_ERROR, "%s value '%s' unknown, assuming 'blend'",
+                  GRPC_ARG_OPTIMIZATION_TARGET,
+                  channel_args->args[i].value.string);
+        }
       } else {
         static const struct {
           const char *channel_arg_name;
@@ -528,6 +546,11 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
     }
   }
 
+  GRPC_CLOSURE_INIT(&t->write_action, write_action, t,
+                    t->opt_target == GRPC_CHTTP2_OPTIMIZE_FOR_THROUGHPUT
+                        ? grpc_executor_scheduler
+                        : grpc_schedule_on_exec_ctx);
+
   t->ping_state.pings_before_data_required =
       t->ping_policy.max_pings_without_data;
   t->ping_state.is_delayed_ping_timer_set = false;

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

@@ -66,6 +66,11 @@ typedef enum {
   GRPC_CHTTP2_PING_TYPE_COUNT /* must be last */
 } grpc_chttp2_ping_type;
 
+typedef enum {
+  GRPC_CHTTP2_OPTIMIZE_FOR_LATENCY,
+  GRPC_CHTTP2_OPTIMIZE_FOR_THROUGHPUT,
+} grpc_chttp2_optimization_target;
+
 typedef enum {
   GRPC_CHTTP2_PCL_INITIATE = 0,
   GRPC_CHTTP2_PCL_NEXT,
@@ -229,6 +234,8 @@ struct grpc_chttp2_transport {
   /** should we probe bdp? */
   bool enable_bdp_probe;
 
+  grpc_chttp2_optimization_target opt_target;
+
   /** various lists of streams */
   grpc_chttp2_stream_list lists[STREAM_LIST_COUNT];
 

tools/run_tests/performance/scenario_config.py

@@ -120,12 +120,14 @@ def _ping_pong_scenario(name, rpc_type,
         'closed_loop': {}
       },
       'histogram_params': HISTOGRAM_PARAMS,
+      'channel_args': [],
     },
     'server_config': {
       'server_type': server_type,
       'security_params': _get_secargs(secure),
       'async_server_threads': async_server_threads,
       'threads_per_cq': server_threads_per_cq,
+      'channel_args': [],
     },
     'warmup_seconds': warmup_seconds,
     'benchmark_seconds': BENCHMARK_SECONDS
@@ -139,6 +141,8 @@ def _ping_pong_scenario(name, rpc_type,
 
   scenario['client_config']['payload_config'] = _payload_type(use_generic_payload, req_size, resp_size)
 
+  optimization_target = 'blend'
+
   if unconstrained_client:
     outstanding_calls = outstanding if outstanding is not None else OUTSTANDING_REQUESTS[unconstrained_client]
     # clamp buffer usage to something reasonable (16 gig for now)
@@ -152,10 +156,19 @@ def _ping_pong_scenario(name, rpc_type,
     scenario['client_config']['outstanding_rpcs_per_channel'] = deep
     scenario['client_config']['client_channels'] = wide
     scenario['client_config']['async_client_threads'] = 0
+    optimization_target = 'throughput'
   else:
     scenario['client_config']['outstanding_rpcs_per_channel'] = 1
     scenario['client_config']['client_channels'] = 1
     scenario['client_config']['async_client_threads'] = 1
+    optimization_target = 'latency'
+
+  optimization_channel_arg = {
+    'name': 'grpc.optimization_target',
+    'str_value': optimization_target
+  }
+  scenario['client_config']['channel_args'].append(optimization_channel_arg)
+  scenario['server_config']['channel_args'].append(optimization_channel_arg)
 
   if messages_per_stream:
     scenario['client_config']['messages_per_stream'] = messages_per_stream