From a8d680923b66843497ed3021100c457b182378da Mon Sep 17 00:00:00 2001
From: Craig Tiller <ctiller@google.com>
Date: Tue, 17 Nov 2015 08:02:29 -0800
Subject: [PATCH] Add a (temporary) facility to tune stream read-ahead size
---
include/grpc/grpc.h | 5 +++++
src/core/transport/chttp2/internal.h | 3 +++
src/core/transport/chttp2_transport.c | 23 ++++++++++++++++++-----
3 files changed, 26 insertions(+), 5 deletions(-)
diff --git a/include/grpc/grpc.h b/include/grpc/grpc.h
index 191ad5db1e..05c1b4c776 100644
--- a/include/grpc/grpc.h
+++ b/include/grpc/grpc.h
@@ -127,6 +127,11 @@ typedef struct {
/** Initial sequence number for http2 transports */
#define GRPC_ARG_HTTP2_INITIAL_SEQUENCE_NUMBER \
"grpc.http2.initial_sequence_number"
+/** Amount to read ahead on individual streams. Defaults to 64kb, larger
+ values can help throughput on high-latency connections.
+ NOTE: at some point we'd like to auto-tune this, and this parameter
+ will become a no-op. */
+#define GRPC_ARG_HTTP2_STREAM_LOOKAHEAD_BYTES "grpc.http2.lookahead_bytes"
/** Default authority to pass if none specified on call construction */
#define GRPC_ARG_DEFAULT_AUTHORITY "grpc.default_authority"
/** Primary user agent: goes at the start of the user-agent metadata
diff --git a/src/core/transport/chttp2/internal.h b/src/core/transport/chttp2/internal.h
index 2d0cb4abdb..972347967b 100644
--- a/src/core/transport/chttp2/internal.h
+++ b/src/core/transport/chttp2/internal.h
@@ -191,6 +191,9 @@ typedef struct {
copied to next_stream_id in parsing when parsing commences */
gpr_uint32 next_stream_id;
+ /** how far to lookahead in a stream? */
+ gpr_uint32 stream_lookahead;
+
/** last received stream id */
gpr_uint32 last_incoming_stream_id;
diff --git a/src/core/transport/chttp2_transport.c b/src/core/transport/chttp2_transport.c
index f62294c7c5..98a0186292 100644
--- a/src/core/transport/chttp2_transport.c
+++ b/src/core/transport/chttp2_transport.c
@@ -52,7 +52,6 @@
#include "src/core/transport/transport_impl.h"
#define DEFAULT_WINDOW 65535
-#define GRPC_CHTTP2_STREAM_LOOKAHEAD DEFAULT_WINDOW
#define DEFAULT_CONNECTION_WINDOW_TARGET (1024 * 1024)
#define MAX_WINDOW 0x7fffffffu
@@ -245,6 +244,7 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
t->global.is_client = is_client;
t->writing.outgoing_window = DEFAULT_WINDOW;
t->parsing.incoming_window = DEFAULT_WINDOW;
+ t->global.stream_lookahead = DEFAULT_WINDOW;
t->global.connection_window_target = DEFAULT_CONNECTION_WINDOW_TARGET;
t->global.ping_counter = 1;
t->global.pings.next = t->global.pings.prev = &t->global.pings;
@@ -338,6 +338,18 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
t->global.next_stream_id =
(gpr_uint32)channel_args->args[i].value.integer;
}
+ } else if (0 == strcmp(channel_args->args[i].key,
+ GRPC_ARG_HTTP2_STREAM_LOOKAHEAD_BYTES)) {
+ if (channel_args->args[i].type != GRPC_ARG_INTEGER) {
+ gpr_log(GPR_ERROR, "%s: must be an integer",
+ GRPC_ARG_HTTP2_STREAM_LOOKAHEAD_BYTES);
+ } else if (channel_args->args[i].value.integer <= 5) {
+ gpr_log(GPR_ERROR, "%s: must be at least 5",
+ GRPC_ARG_HTTP2_STREAM_LOOKAHEAD_BYTES);
+ } else {
+ t->global.stream_lookahead =
+ (gpr_uint32)channel_args->args[i].value.integer;
+ }
}
}
}
@@ -1372,8 +1384,8 @@ static void incoming_byte_stream_update_flow_control(
gpr_uint32 max_recv_bytes;
/* clamp max recv hint to an allowable size */
- if (max_size_hint >= GPR_UINT32_MAX - GRPC_CHTTP2_STREAM_LOOKAHEAD) {
- max_recv_bytes = GPR_UINT32_MAX - GRPC_CHTTP2_STREAM_LOOKAHEAD;
+ if (max_size_hint >= GPR_UINT32_MAX - transport_global->stream_lookahead) {
+ max_recv_bytes = GPR_UINT32_MAX - transport_global->stream_lookahead;
} else {
max_recv_bytes = (gpr_uint32)max_size_hint;
}
@@ -1386,8 +1398,9 @@ static void incoming_byte_stream_update_flow_control(
}
/* add some small lookahead to keep pipelines flowing */
- GPR_ASSERT(max_recv_bytes <= GPR_UINT32_MAX - GRPC_CHTTP2_STREAM_LOOKAHEAD);
- max_recv_bytes += GRPC_CHTTP2_STREAM_LOOKAHEAD;
+ GPR_ASSERT(max_recv_bytes <=
+ GPR_UINT32_MAX - transport_global->stream_lookahead);
+ max_recv_bytes += transport_global->stream_lookahead;
if (stream_global->max_recv_bytes < max_recv_bytes) {
gpr_uint32 add_max_recv_bytes =
max_recv_bytes - stream_global->max_recv_bytes;
--
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