emrekultursay created this revision.
Herald added subscribers: lldb-commits, mgrang.
Herald added a project: LLDB.
When connecting to Android, LLDB calls adb#Shell 5 times. At each call,
a TCP connection to "localhost:port" needs to be established. On hosts
that support IPv4 and IPv6, the "localhost" host can map to two
addresses.
It seems like IPv6 typically becomes the addresses[0], and then trying
to connect to it gets rejected (WSAECONNREFUSED), and then the IPv4 one
at addresses[1] succeeds.
Trying to connect to IPv6 first wastes up to 2 seconds per call on
Windows. The adb CLI client also uses an IPv4-first approach.
On Windows, this CL brings total of ~10 second improvement in LLDB
attach latency to Android devices.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D79757
Files:
lldb/source/Host/common/TCPSocket.cpp
Index: lldb/source/Host/common/TCPSocket.cpp
===================================================================
--- lldb/source/Host/common/TCPSocket.cpp
+++ lldb/source/Host/common/TCPSocket.cpp
@@ -162,6 +162,12 @@
std::vector<SocketAddress> addresses = SocketAddress::GetAddressInfo(
host_str.c_str(), nullptr, AF_UNSPEC, SOCK_STREAM, IPPROTO_TCP);
+ // IPv4 is more likely to succeed than IPv6. To avoid costly retries,
+ // we sort based on family to prioritize IPv4 over IPv6.
+ std::sort(addresses.begin(), addresses.end(),
+ [](SocketAddress a, SocketAddress b) {
+ return a.GetFamily() < b.GetFamily();
+ });
for (SocketAddress &address : addresses) {
error = CreateSocket(address.GetFamily());
if (error.Fail())
Index: lldb/source/Host/common/TCPSocket.cpp
===================================================================
--- lldb/source/Host/common/TCPSocket.cpp
+++ lldb/source/Host/common/TCPSocket.cpp
@@ -162,6 +162,12 @@
std::vector<SocketAddress> addresses = SocketAddress::GetAddressInfo(
host_str.c_str(), nullptr, AF_UNSPEC, SOCK_STREAM, IPPROTO_TCP);
+ // IPv4 is more likely to succeed than IPv6. To avoid costly retries,
+ // we sort based on family to prioritize IPv4 over IPv6.
+ std::sort(addresses.begin(), addresses.end(),
+ [](SocketAddress a, SocketAddress b) {
+ return a.GetFamily() < b.GetFamily();
+ });
for (SocketAddress &address : addresses) {
error = CreateSocket(address.GetFamily());
if (error.Fail())
_______________________________________________
lldb-commits mailing list
lldb-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
