[Lldb-commits] [PATCH] D93895: Implement vAttachWait in lldb-server

Greg Clayton via Phabricator via lldb-commits lldb-commits at lists.llvm.org
Mon Jan 4 14:19:41 PST 2021

clayborg added a comment.

Patch looks good, just a question of what timeout to use by default and possible adding an option to lldb-server in case users want faster or slower polling.

Comment at: lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp:344
+  // TODO: Make the polling interval configurable.
+  std::chrono::milliseconds polling_interval = std::chrono::seconds(1);
We probably want this to be quite a bit shorter than 1 second. Why? Because if you don't find the process right away, 1 second is a long time for the system to wait and your program can execute quite a few instructions in 1 second. By the time you attach, you might have missed your breakpoint at main. Nothing will guarantee hitting a breakpoint, but I would suggest making a smaller timeout, maybe like 1 millisecond. It would be good to benchmark this a bit by waiting for a process and not launching a new process to see how much CPU lldb-server takes up with a shorter timeout.

Adding a command line option might be nice is someone could specify "--wait-poll-msec 0" to constantly poll the system as fast as possible in case they do need to catch the process as early as possible.

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