relnote: Cache-align the encryption buffer in QuicPacketCreator::SerializePacket.

net/quic/quic_packet_creator.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/quic_packet_creator.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/logging.h"
@@ skipping 432 matching lines @@
   MaybeAddPadding();
 
   DCHECK_GE(max_plaintext_size_, packet_size_);
   // ACK Frames will be truncated due to length only if they're the only frame
   // in the packet, and if packet_size_ was set to max_plaintext_size_. If
   // truncation due to length occurred, then GetSerializedFrameLength will have
   // returned all bytes free.
   bool possibly_truncated_by_length = packet_size_ == max_plaintext_size_ &&
                                       queued_frames_.size() == 1 &&
                                       queued_frames_.back().type == ACK_FRAME;
-  char buffer[kMaxPacketSize];
+  // The optimized encryption algorithm implementations run faster when
+  // operating on aligned memory.
+  // TODO(rtenneti): Change the default 64 alignas value (used the default
+  // value from CACHELINE_SIZE).
+  ALIGNAS(64) char buffer[kMaxPacketSize];
   scoped_ptr<QuicPacket> packet;
   // Use the packet_size_ instead of the buffer size to ensure smaller
   // packet sizes are properly used.
   scoped_ptr<char[]> large_buffer;
   if (packet_size_ <= kMaxPacketSize) {
     packet.reset(
         framer_->BuildDataPacket(header, queued_frames_, buffer, packet_size_));
   } else {
     large_buffer.reset(new char[packet_size_]);
     packet.reset(framer_->BuildDataPacket(header, queued_frames_,
@@ skipping 172 matching lines @@
     // Don't pad full packets.
     return;
   }
 
   QuicPaddingFrame padding;
   bool success = AddFrame(QuicFrame(&padding), false, false, nullptr);
   DCHECK(success);
 }
 
 }  // namespace net