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Batch unref metadata in HTTP/2 stream encoder

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Moves us from one metadata lock per metadata element to one metadata
lock per HTTP/2 frame output.
pull/1277/head
Craig Tiller 10 years ago
parent 7b3b058b57
commit fe0104a160
3 changed files with 73 additions and 33 deletions
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  1. 80
      src/core/transport/chttp2/stream_encoder.c
  2. 14
      src/core/transport/metadata.c
  3. 12
      src/core/transport/metadata.h

80
src/core/transport/chttp2/stream_encoder.c
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@ -171,13 +171,15 @@ static gpr_uint8 *add_tiny_header_data(framer_state *st, int len) {
return gpr_slice_buffer_tiny_add(st->output, len);
}
static void add_elem(grpc_chttp2_hpack_compressor *c, grpc_mdelem *elem) {
/* add an element to the decoder table: returns metadata element to unref */
static grpc_mdelem *add_elem(grpc_chttp2_hpack_compressor *c,
grpc_mdelem *elem) {
gpr_uint32 key_hash = elem->key->hash;
gpr_uint32 elem_hash = GRPC_MDSTR_KV_HASH(key_hash, elem->value->hash);
gpr_uint32 new_index = c->tail_remote_index + c->table_elems + 1;
gpr_uint32 elem_size = 32 + GPR_SLICE_LENGTH(elem->key->slice) +
GPR_SLICE_LENGTH(elem->value->slice);
int drop_ref;
grpc_mdelem *elem_to_unref = (void *)1;
/* Reserve space for this element in the remote table: if this overflows
the current table, drop elements until it fits, matching the decompressor
@ -204,34 +206,32 @@ static void add_elem(grpc_chttp2_hpack_compressor *c, grpc_mdelem *elem) {
if (c->entries_elems[HASH_FRAGMENT_2(elem_hash)] == elem) {
/* already there: update with new index */
c->indices_elems[HASH_FRAGMENT_2(elem_hash)] = new_index;
drop_ref = 1;
elem_to_unref = elem;
} else if (c->entries_elems[HASH_FRAGMENT_3(elem_hash)] == elem) {
/* already there (cuckoo): update with new index */
c->indices_elems[HASH_FRAGMENT_3(elem_hash)] = new_index;
drop_ref = 1;
elem_to_unref = elem;
} else if (c->entries_elems[HASH_FRAGMENT_2(elem_hash)] == NULL) {
/* not there, but a free element: add */
c->entries_elems[HASH_FRAGMENT_2(elem_hash)] = elem;
c->indices_elems[HASH_FRAGMENT_2(elem_hash)] = new_index;
drop_ref = 0;
elem_to_unref = NULL;
} else if (c->entries_elems[HASH_FRAGMENT_3(elem_hash)] == NULL) {
/* not there (cuckoo), but a free element: add */
c->entries_elems[HASH_FRAGMENT_3(elem_hash)] = elem;
c->indices_elems[HASH_FRAGMENT_3(elem_hash)] = new_index;
drop_ref = 0;
elem_to_unref = NULL;
} else if (c->indices_elems[HASH_FRAGMENT_2(elem_hash)] <
c->indices_elems[HASH_FRAGMENT_3(elem_hash)]) {
/* not there: replace oldest */
grpc_mdelem_unref(c->entries_elems[HASH_FRAGMENT_2(elem_hash)]);
elem_to_unref = c->entries_elems[HASH_FRAGMENT_2(elem_hash)];
c->entries_elems[HASH_FRAGMENT_2(elem_hash)] = elem;
c->indices_elems[HASH_FRAGMENT_2(elem_hash)] = new_index;
drop_ref = 0;
} else {
/* not there: replace oldest */
grpc_mdelem_unref(c->entries_elems[HASH_FRAGMENT_3(elem_hash)]);
elem_to_unref = c->entries_elems[HASH_FRAGMENT_3(elem_hash)];
c->entries_elems[HASH_FRAGMENT_3(elem_hash)] = elem;
c->indices_elems[HASH_FRAGMENT_3(elem_hash)] = new_index;
drop_ref = 0;
}
/* do exactly the same for the key (so we can find by that again too) */
@ -257,9 +257,7 @@ static void add_elem(grpc_chttp2_hpack_compressor *c, grpc_mdelem *elem) {
c->indices_keys[HASH_FRAGMENT_3(key_hash)] = new_index;
}
if (drop_ref) {
grpc_mdelem_unref(elem);
}
return elem_to_unref;
}
static void emit_indexed(grpc_chttp2_hpack_compressor *c, gpr_uint32 index,
@ -348,9 +346,9 @@ static gpr_uint32 dynidx(grpc_chttp2_hpack_compressor *c, gpr_uint32 index) {
c->table_elems - index;
}
/* encode an mdelem, taking ownership of it */
static void hpack_enc(grpc_chttp2_hpack_compressor *c, grpc_mdelem *elem,
framer_state *st) {
/* encode an mdelem; returns metadata element to unref */
static grpc_mdelem *hpack_enc(grpc_chttp2_hpack_compressor *c,
grpc_mdelem *elem, framer_state *st) {
gpr_uint32 key_hash = elem->key->hash;
gpr_uint32 elem_hash = GRPC_MDSTR_KV_HASH(key_hash, elem->value->hash);
size_t decoder_space_usage;
@ -366,8 +364,7 @@ static void hpack_enc(grpc_chttp2_hpack_compressor *c, grpc_mdelem *elem,
/* HIT: complete element (first cuckoo hash) */
emit_indexed(c, dynidx(c, c->indices_elems[HASH_FRAGMENT_2(elem_hash)]),
st);
grpc_mdelem_unref(elem);
return;
return elem;
}
if (c->entries_elems[HASH_FRAGMENT_3(elem_hash)] == elem &&
@ -375,8 +372,7 @@ static void hpack_enc(grpc_chttp2_hpack_compressor *c, grpc_mdelem *elem,
/* HIT: complete element (second cuckoo hash) */
emit_indexed(c, dynidx(c, c->indices_elems[HASH_FRAGMENT_3(elem_hash)]),
st);
grpc_mdelem_unref(elem);
return;
return elem;
}
/* should this elem be in the table? */
@ -394,12 +390,12 @@ static void hpack_enc(grpc_chttp2_hpack_compressor *c, grpc_mdelem *elem,
/* HIT: key (first cuckoo hash) */
if (should_add_elem) {
emit_lithdr_incidx(c, dynidx(c, indices_key), elem, st);
add_elem(c, elem);
return add_elem(c, elem);
} else {
emit_lithdr_noidx(c, dynidx(c, indices_key), elem, st);
grpc_mdelem_unref(elem);
return elem;
}
return;
abort();
}
indices_key = c->indices_keys[HASH_FRAGMENT_3(key_hash)];
@ -408,23 +404,24 @@ static void hpack_enc(grpc_chttp2_hpack_compressor *c, grpc_mdelem *elem,
/* HIT: key (first cuckoo hash) */
if (should_add_elem) {
emit_lithdr_incidx(c, dynidx(c, indices_key), elem, st);
add_elem(c, elem);
return add_elem(c, elem);
} else {
emit_lithdr_noidx(c, dynidx(c, indices_key), elem, st);
grpc_mdelem_unref(elem);
return elem;
}
return;
abort();
}
/* no elem, key in the table... fall back to literal emission */
if (should_add_elem) {
emit_lithdr_incidx_v(c, elem, st);
add_elem(c, elem);
return add_elem(c, elem);
} else {
emit_lithdr_noidx_v(c, elem, st);
grpc_mdelem_unref(elem);
return elem;
}
abort();
}
#define STRLEN_LIT(x) (sizeof(x) - 1)
@ -433,11 +430,13 @@ static void hpack_enc(grpc_chttp2_hpack_compressor *c, grpc_mdelem *elem,
static void deadline_enc(grpc_chttp2_hpack_compressor *c, gpr_timespec deadline,
framer_state *st) {
char timeout_str[GRPC_CHTTP2_TIMEOUT_ENCODE_MIN_BUFSIZE];
grpc_mdelem *mdelem;
grpc_chttp2_encode_timeout(gpr_time_sub(deadline, gpr_now()), timeout_str);
hpack_enc(c, grpc_mdelem_from_metadata_strings(
c->mdctx, grpc_mdstr_ref(c->timeout_key_str),
grpc_mdstr_from_string(c->mdctx, timeout_str)),
st);
mdelem = grpc_mdelem_from_metadata_strings(
c->mdctx, grpc_mdstr_ref(c->timeout_key_str),
grpc_mdstr_from_string(c->mdctx, timeout_str));
mdelem = hpack_enc(c, mdelem, st);
if (mdelem) grpc_mdelem_unref(mdelem);
}
gpr_slice grpc_chttp2_data_frame_create_empty_close(gpr_uint32 id) {
@ -542,6 +541,9 @@ void grpc_chttp2_encode(grpc_stream_op *ops, size_t ops_count, int eof,
grpc_stream_op *op;
gpr_uint32 max_take_size;
gpr_uint32 curop = 0;
gpr_uint32 unref_op;
grpc_mdctx *mdctx = compressor->mdctx;
int need_unref = 0;
GPR_ASSERT(stream_id != 0);
@ -564,7 +566,8 @@ void grpc_chttp2_encode(grpc_stream_op *ops, size_t ops_count, int eof,
curop++;
break;
case GRPC_OP_METADATA:
hpack_enc(compressor, op->data.metadata, &st);
op->data.metadata = hpack_enc(compressor, op->data.metadata, &st);
need_unref |= op->data.metadata != NULL;
curop++;
break;
case GRPC_OP_DEADLINE:
@ -601,4 +604,15 @@ void grpc_chttp2_encode(grpc_stream_op *ops, size_t ops_count, int eof,
begin_frame(&st, DATA);
}
finish_frame(&st, 1, eof);
if (need_unref) {
grpc_mdctx_lock(mdctx);
for (unref_op = 0; unref_op < curop; unref_op++) {
op = &ops[unref_op];
if (op->type != GRPC_OP_METADATA) continue;
if (!op->data.metadata) continue;
grpc_mdctx_locked_mdelem_unref(mdctx, op->data.metadata);
}
grpc_mdctx_unlock(mdctx);
}
}

14
src/core/transport/metadata.c
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@ -550,3 +550,17 @@ gpr_slice grpc_mdstr_as_base64_encoded_and_huffman_compressed(grpc_mdstr *gs) {
unlock(ctx);
return slice;
}
void grpc_mdctx_lock(grpc_mdctx *ctx) { lock(ctx); }
void grpc_mdctx_locked_mdelem_unref(grpc_mdctx *ctx, grpc_mdelem *gmd) {
internal_metadata *md = (internal_metadata *)gmd;
grpc_mdctx *elem_ctx = md->context;
GPR_ASSERT(md->refs);
GPR_ASSERT(ctx == elem_ctx);
if (0 == --md->refs) {
ctx->mdtab_free++;
}
}
void grpc_mdctx_unlock(grpc_mdctx *ctx) { unlock(ctx); }

12
src/core/transport/metadata.h
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@ -135,6 +135,18 @@ void grpc_mdelem_unref(grpc_mdelem *md);
Does not promise that the returned string has no embedded nulls however. */
const char *grpc_mdstr_as_c_string(grpc_mdstr *s);
/* Batch mode metadata functions.
These API's have equivalents above, but allow taking the mdctx just once,
performing a bunch of work, and then leaving the mdctx. */
/* Lock the metadata context: it's only safe to call _locked_ functions against
this context from the calling thread until grpc_mdctx_unlock is called */
void grpc_mdctx_lock(grpc_mdctx *ctx);
/* Unref a metadata element */
void grpc_mdctx_locked_mdelem_unref(grpc_mdctx *ctx, grpc_mdelem *elem);
/* Unlock the metadata context */
void grpc_mdctx_unlock(grpc_mdctx *ctx);
#define GRPC_MDSTR_KV_HASH(k_hash, v_hash) (GPR_ROTL((k_hash), 2) ^ (v_hash))
#endif /* GRPC_INTERNAL_CORE_TRANSPORT_METADATA_H */

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