Deprecate --gfe2_reloadable_flag_quic_packet_creator_prefetch.

net/quic/quic_packet_creator.cc

Index: net/quic/quic_packet_creator.cc
diff --git a/net/quic/quic_packet_creator.cc b/net/quic/quic_packet_creator.cc
index 7c1cadef4a8ae97ce69fbe8e4f69536e1be0ca39..c89058dcff862b60f17b427d490094c1c5f19912 100644
--- a/net/quic/quic_packet_creator.cc
+++ b/net/quic/quic_packet_creator.cc
@@ -347,54 +347,43 @@ void QuicPacketCreator::CopyToBuffer(QuicIOVector iov,
   }
   DCHECK_LE(iovnum, iov.iov_count);
   DCHECK_LE(iov_offset, iov.iov[iovnum].iov_len);
-  if (FLAGS_quic_packet_creator_prefetch) {
-    if (iovnum >= iov.iov_count || length == 0) {
-      return;
-    }
+  if (iovnum >= iov.iov_count || length == 0) {
+    return;
+  }
 
-    // Unroll the first iteration that handles iov_offset.
-    const size_t iov_available = iov.iov[iovnum].iov_len - iov_offset;
-    size_t copy_len = min(length, iov_available);
-
-    // Try to prefetch the next iov if there is at least one more after the
-    // current. Otherwise, it looks like an irregular access that the hardware
-    // prefetcher won't speculatively prefetch. Only prefetch one iov because
-    // generally, the iov_offset is not 0, input iov consists of 2K buffers and
-    // the output buffer is ~1.4K.
-    if (copy_len == iov_available && iovnum + 1 < iov.iov_count) {
-      // TODO(ckrasic) - this is unused without prefetch()
-      // char* next_base = static_cast<char*>(iov.iov[iovnum + 1].iov_base);
-      // Prefetch 2 cachelines worth of data to get the prefetcher started;
-      // leave it to the hardware prefetcher after that.
+  // Unroll the first iteration that handles iov_offset.
+  const size_t iov_available = iov.iov[iovnum].iov_len - iov_offset;
+  size_t copy_len = min(length, iov_available);
+
+  // Try to prefetch the next iov if there is at least one more after the
+  // current. Otherwise, it looks like an irregular access that the hardware
+  // prefetcher won't speculatively prefetch. Only prefetch one iov because
+  // generally, the iov_offset is not 0, input iov consists of 2K buffers and
+  // the output buffer is ~1.4K.
+  if (copy_len == iov_available && iovnum + 1 < iov.iov_count) {
+    // TODO(ckrasic) - this is unused without prefetch()
+    // char* next_base = static_cast<char*>(iov.iov[iovnum + 1].iov_base);
+    // char* next_base = static_cast<char*>(iov.iov[iovnum + 1].iov_base);
+    // Prefetch 2 cachelines worth of data to get the prefetcher started; leave
+    // it to the hardware prefetcher after that.
+    // TODO(ckrasic) - investigate what to do about prefetch directives.
+    // prefetch(next_base, PREFETCH_HINT_T0);
+    if (iov.iov[iovnum + 1].iov_len >= 64) {
       // TODO(ckrasic) - investigate what to do about prefetch directives.
-      // prefetch(next_base, PREFETCH_HINT_T0);
-      if (iov.iov[iovnum + 1].iov_len >= 64) {
-        // TODO(ckrasic) - investigate what to do about prefetch directives.
-        // prefetch(next_base + CACHELINE_SIZE, PREFETCH_HINT_T0);
-      }
+      // prefetch(next_base + CACHELINE_SIZE, PREFETCH_HINT_T0);
     }
+  }
 
-    const char* src = static_cast<char*>(iov.iov[iovnum].iov_base) + iov_offset;
-    while (true) {
-      memcpy(buffer, src, copy_len);
-      length -= copy_len;
-      buffer += copy_len;
-      if (length == 0 || ++iovnum >= iov.iov_count) {
-        break;
-      }
-      src = static_cast<char*>(iov.iov[iovnum].iov_base);
-      copy_len = min(length, iov.iov[iovnum].iov_len);
-    }
-  } else {
-    while (iovnum < iov.iov_count && length > 0) {
-      const size_t copy_len = min(length, iov.iov[iovnum].iov_len - iov_offset);
-      memcpy(buffer, static_cast<char*>(iov.iov[iovnum].iov_base) + iov_offset,
-             copy_len);
-      iov_offset = 0;
-      length -= copy_len;
-      buffer += copy_len;
-      ++iovnum;
+  const char* src = static_cast<char*>(iov.iov[iovnum].iov_base) + iov_offset;
+  while (true) {
+    memcpy(buffer, src, copy_len);
+    length -= copy_len;
+    buffer += copy_len;
+    if (length == 0 || ++iovnum >= iov.iov_count) {
+      break;
     }
+    src = static_cast<char*>(iov.iov[iovnum].iov_base);
+    copy_len = min(length, iov.iov[iovnum].iov_len);
   }
   LOG_IF(DFATAL, length > 0) << "Failed to copy entire length to buffer.";
 }