Increase HPACK table size up to the optimal size if clients allow it.

This CL lands server change 133042402 by yasong@.

BUG=488484

Review-Url: https://codereview.chromium.org/2348603003
Cr-Commit-Position: refs/heads/master@{#419235}

net/spdy/hpack/hpack_header_table.cc

@@ -9,6 +9,7 @@
 #include "base/logging.h"
 #include "net/spdy/hpack/hpack_constants.h"
 #include "net/spdy/hpack/hpack_static_table.h"
+#include "net/spdy/spdy_flags.h"
 
 namespace net {
 
@@ -125,7 +126,11 @@ void HpackHeaderTable::SetMaxSize(size_t max_size) {
 
 void HpackHeaderTable::SetSettingsHeaderTableSize(size_t settings_size) {
   settings_size_bound_ = settings_size;
-  if (settings_size_bound_ < max_size_) {
+  if (!FLAGS_chromium_reloadable_flag_increase_hpack_table_size) {
+    if (settings_size_bound_ < max_size_) {
+      SetMaxSize(settings_size_bound_);
+    }
+  } else {
     SetMaxSize(settings_size_bound_);
   }
 }

net/spdy/hpack/hpack_header_table_test.cc

@@ -12,6 +12,7 @@
 #include "base/macros.h"
 #include "net/spdy/hpack/hpack_constants.h"
 #include "net/spdy/hpack/hpack_entry.h"
+#include "net/spdy/spdy_flags.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace net {
@@ -258,6 +259,41 @@ TEST_F(HpackHeaderTableTest, EntryIndexing) {
 }
 
 TEST_F(HpackHeaderTableTest, SetSizes) {
+  FLAGS_chromium_reloadable_flag_increase_hpack_table_size = true;
+  string key = "key", value = "value";
+  const HpackEntry* entry1 = table_.TryAddEntry(key, value);
+  const HpackEntry* entry2 = table_.TryAddEntry(key, value);
+  const HpackEntry* entry3 = table_.TryAddEntry(key, value);
+
+  // Set exactly large enough. No Evictions.
+  size_t max_size = entry1->Size() + entry2->Size() + entry3->Size();
+  table_.SetMaxSize(max_size);
+  EXPECT_EQ(3u, peer_.dynamic_entries().size());
+
+  // Set just too small. One eviction.
+  max_size = entry1->Size() + entry2->Size() + entry3->Size() - 1;
+  table_.SetMaxSize(max_size);
+  EXPECT_EQ(2u, peer_.dynamic_entries().size());
+
+  // Changing SETTINGS_HEADER_TABLE_SIZE.
+  EXPECT_EQ(kDefaultHeaderTableSizeSetting, table_.settings_size_bound());
+  // In production, the size passed to SetSettingsHeaderTableSize is never
+  // larger than table_.settings_size_bound().
+  table_.SetSettingsHeaderTableSize(kDefaultHeaderTableSizeSetting * 3 + 1);
+  EXPECT_EQ(kDefaultHeaderTableSizeSetting * 3 + 1, table_.max_size());
+
+  // SETTINGS_HEADER_TABLE_SIZE upper-bounds |table_.max_size()|,
+  // and will force evictions.
+  max_size = entry3->Size() - 1;
+  table_.SetSettingsHeaderTableSize(max_size);
+  EXPECT_EQ(max_size, table_.max_size());
+  EXPECT_EQ(max_size, table_.settings_size_bound());
+  EXPECT_EQ(0u, peer_.dynamic_entries().size());
+}
+
+TEST_F(HpackHeaderTableTest, SetSizesOld) {
+  FLAGS_chromium_reloadable_flag_increase_hpack_table_size = false;
+
   string key = "key", value = "value";
   const HpackEntry* entry1 = table_.TryAddEntry(key, value);
   const HpackEntry* entry2 = table_.TryAddEntry(key, value);

net/spdy/spdy_flags.cc

@@ -13,6 +13,10 @@ bool FLAGS_chromium_http2_flag_spdy_framer_use_new_methods4 = true;
 // Use SpdyHeaderBlock::AppendValueOrAddHeader when adding to headers.
 bool FLAGS_chromium_http2_flag_use_new_spdy_header_block_header_joining = true;
 
+// If true, increase HPACK table size up to optimal size kOptTableSize if
+// clients allow it.
+bool FLAGS_chromium_reloadable_flag_increase_hpack_table_size = false;
+
 // Use NestedSpdyFramerDecoder.
 bool FLAGS_use_nested_spdy_framer_decoder = false;
 

net/spdy/spdy_flags.h

@@ -13,6 +13,8 @@ NET_EXPORT_PRIVATE extern bool
     FLAGS_chromium_http2_flag_spdy_framer_use_new_methods4;
 NET_EXPORT_PRIVATE extern bool
     FLAGS_chromium_http2_flag_use_new_spdy_header_block_header_joining;
+NET_EXPORT_PRIVATE extern bool
+    FLAGS_chromium_reloadable_flag_increase_hpack_table_size;
 NET_EXPORT_PRIVATE extern bool FLAGS_use_nested_spdy_framer_decoder;
 
 }  // namespace net