diff --git a/src/core/surface/call.c b/src/core/surface/call.c
index 30b15ce37fa71d3c43f89fbb2dce00409b618e7e..93b3a54ea451d71507bde15e0beaf6f3264d454a 100644
--- a/src/core/surface/call.c
+++ b/src/core/surface/call.c
@@ -820,7 +820,6 @@ static int fill_send_ops(grpc_call *call, grpc_transport_op *op) {
grpc_ioreq_data data;
grpc_metadata_batch mdb;
size_t i;
- char status_str[GPR_LTOA_MIN_BUFSIZE];
GPR_ASSERT(op->send_ops == NULL);
switch (call->write_state) {
@@ -865,13 +864,10 @@ static int fill_send_ops(grpc_call *call, grpc_transport_op *op) {
/* send status */
/* TODO(ctiller): cache common status values */
data = call->request_data[GRPC_IOREQ_SEND_STATUS];
- gpr_ltoa(data.send_status.code, status_str);
grpc_metadata_batch_add_tail(
&mdb, &call->status_link,
- grpc_mdelem_from_metadata_strings(
- call->metadata_context,
- grpc_mdstr_ref(grpc_channel_get_status_string(call->channel)),
- grpc_mdstr_from_string(call->metadata_context, status_str)));
+ grpc_channel_get_reffed_status_elem(call->channel,
+ data.send_status.code));
if (data.send_status.details) {
grpc_metadata_batch_add_tail(
&mdb, &call->details_link,
diff --git a/src/core/surface/channel.c b/src/core/surface/channel.c
index 947011c613f61058cce22af56501c913cb1f724b..9175ad0572ac5fea706e10e728e9891b37c853fd 100644
--- a/src/core/surface/channel.c
+++ b/src/core/surface/channel.c
@@ -37,12 +37,20 @@
#include <string.h>
#include "src/core/iomgr/iomgr.h"
+#include "src/core/support/string.h"
#include "src/core/surface/call.h"
#include "src/core/surface/client.h"
#include "src/core/surface/init.h"
#include <grpc/support/alloc.h>
#include <grpc/support/log.h>
+/** Cache grpc-status: X mdelems for X = 0..NUM_CACHED_STATUS_ELEMS.
+ * Avoids needing to take a metadata context lock for sending status
+ * if the status code is <= NUM_CACHED_STATUS_ELEMS.
+ * Sized to allow the most commonly used codes to fit in
+ * (OK, Cancelled, Unknown). */
+#define NUM_CACHED_STATUS_ELEMS 3
+
typedef struct registered_call {
grpc_mdelem *path;
grpc_mdelem *authority;
@@ -54,10 +62,13 @@ struct grpc_channel {
gpr_refcount refs;
gpr_uint32 max_message_length;
grpc_mdctx *metadata_context;
+ /** mdstr for the grpc-status key */
grpc_mdstr *grpc_status_string;
grpc_mdstr *grpc_message_string;
grpc_mdstr *path_string;
grpc_mdstr *authority_string;
+ /** mdelem for grpc-status: 0 thru grpc-status: 2 */
+ grpc_mdelem *grpc_status_elem[NUM_CACHED_STATUS_ELEMS];
gpr_mu registered_call_mu;
registered_call *registered_calls;
@@ -88,6 +99,13 @@ grpc_channel *grpc_channel_create_from_filters(
channel->metadata_context = mdctx;
channel->grpc_status_string = grpc_mdstr_from_string(mdctx, "grpc-status");
channel->grpc_message_string = grpc_mdstr_from_string(mdctx, "grpc-message");
+ for (i = 0; i < NUM_CACHED_STATUS_ELEMS; i++) {
+ char buf[GPR_LTOA_MIN_BUFSIZE];
+ gpr_ltoa(i, buf);
+ channel->grpc_status_elem[i] = grpc_mdelem_from_metadata_strings(
+ mdctx, grpc_mdstr_ref(channel->grpc_status_string),
+ grpc_mdstr_from_string(mdctx, buf));
+ }
channel->path_string = grpc_mdstr_from_string(mdctx, ":path");
channel->authority_string = grpc_mdstr_from_string(mdctx, ":authority");
grpc_channel_stack_init(filters, num_filters, args, channel->metadata_context,
@@ -175,7 +193,11 @@ void grpc_channel_internal_ref(grpc_channel *channel) {
static void destroy_channel(void *p, int ok) {
grpc_channel *channel = p;
+ size_t i;
grpc_channel_stack_destroy(CHANNEL_STACK_FROM_CHANNEL(channel));
+ for (i = 0; i < NUM_CACHED_STATUS_ELEMS; i++) {
+ grpc_mdelem_unref(channel->grpc_status_elem[i]);
+ }
grpc_mdstr_unref(channel->grpc_status_string);
grpc_mdstr_unref(channel->grpc_message_string);
grpc_mdstr_unref(channel->path_string);
@@ -235,6 +257,18 @@ grpc_mdstr *grpc_channel_get_status_string(grpc_channel *channel) {
return channel->grpc_status_string;
}
+grpc_mdelem *grpc_channel_get_reffed_status_elem(grpc_channel *channel, int i) {
+ if (i >= 0 && i < NUM_CACHED_STATUS_ELEMS) {
+ return grpc_mdelem_ref(channel->grpc_status_elem[i]);
+ } else {
+ char tmp[GPR_LTOA_MIN_BUFSIZE];
+ gpr_ltoa(i, tmp);
+ return grpc_mdelem_from_metadata_strings(
+ channel->metadata_context, grpc_mdstr_ref(channel->grpc_status_string),
+ grpc_mdstr_from_string(channel->metadata_context, tmp));
+ }
+}
+
grpc_mdstr *grpc_channel_get_message_string(grpc_channel *channel) {
return channel->grpc_message_string;
}
diff --git a/src/core/surface/channel.h b/src/core/surface/channel.h
index 388be357113378423f2aa395130ea3f55c929c08..6d1ed8790060e8d9402e088213e1554a3c484225 100644
--- a/src/core/surface/channel.h
+++ b/src/core/surface/channel.h
@@ -40,8 +40,18 @@ grpc_channel *grpc_channel_create_from_filters(
const grpc_channel_filter **filters, size_t count,
const grpc_channel_args *args, grpc_mdctx *mdctx, int is_client);
+/** Get a (borrowed) pointer to this channels underlying channel stack */
grpc_channel_stack *grpc_channel_get_channel_stack(grpc_channel *channel);
+
+/** Get a (borrowed) pointer to the channel wide metadata context */
grpc_mdctx *grpc_channel_get_metadata_context(grpc_channel *channel);
+
+/** Get a grpc_mdelem of grpc-status: X where X is the numeric value of
+ status_code.
+
+ The returned elem is owned by the caller. */
+grpc_mdelem *grpc_channel_get_reffed_status_elem(grpc_channel *channel,
+ int status_code);
grpc_mdstr *grpc_channel_get_status_string(grpc_channel *channel);
grpc_mdstr *grpc_channel_get_message_string(grpc_channel *channel);
gpr_uint32 grpc_channel_get_max_message_length(grpc_channel *channel);
diff --git a/src/core/transport/metadata.c b/src/core/transport/metadata.c
index c80d67823f548db5b662e55d268452beac770843..e75b449e129cb74b24c219c4ce9d17b2ad217d87 100644
--- a/src/core/transport/metadata.c
+++ b/src/core/transport/metadata.c
@@ -120,7 +120,7 @@ static void unlock(grpc_mdctx *ctx) {
if (ctx->refs == 0) {
/* uncomment if you're having trouble diagnosing an mdelem leak to make
things clearer (slows down destruction a lot, however) */
- gc_mdtab(ctx);
+ /* gc_mdtab(ctx); */
if (ctx->mdtab_count && ctx->mdtab_count == ctx->mdtab_free) {
discard_metadata(ctx);
}