From b7939fe2a0b15ba46faa77552567a2852aea387f Mon Sep 17 00:00:00 2001 From: Thomas De Schampheleire Date: Tue, 1 Jun 2021 16:34:06 +0200 Subject: [PATCH] core: introduce BR2_ENABLE_RUNTIME_DEBUG Some packages have optional runtime assertions, extra traces, or other elements that can help in debugging problems. However, such runtime elements can negatively influence performance. In a test program performing 100K gRPC calls from a client to a local server and receiving the returned response, we see following execution time: - runtime debug enabled: 1065 seconds - runtime debug disabled: 48 seconds This is more than a factor 20 (!) difference. Analysis shows that the problem mostly stems from libabseil-cpp (a dependency of gRPC) which enables mutex deadlock analysis when the preprocessor flag 'NDEBUG' is not set, which adds a 'backtrace()' call on every lock/unlock. Potentially worse, when libunwind is enabled and linked with the test program, 'backtrace()' is not provided by glibc but by libunwind itself. For production systems, users expect good performance out-of-the-box. In the example above, the difference is huge and unless explicitly tested and analyzed, users may not realize that the performance could be much better. Address this problem by introducing a new option BR2_ENABLE_RUNTIME_DEBUG, which can be used by packages or package infrastructures to set the necessary flags. Note that BR2_ENABLE_RUNTIME_DEBUG is orthogonal to BR2_ENABLE_DEBUG: the former changes runtime behavior, while the latter is only expected to add debug symbols to the build. Today, the cmake build system does introduce a runtime impact when BR2_ENABLE_DEBUG is set, but that will be rectified in a subsequent commit. Signed-off-by: Thomas De Schampheleire Acked-by: Arnout Vandecappelle (Essensium/Mind) Reviewed-by: Yann E. MORIN Signed-off-by: Yann E. MORIN --- Config.in | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/Config.in b/Config.in index c65e34bd5e..a008425688 100644 --- a/Config.in +++ b/Config.in @@ -412,6 +412,19 @@ config BR2_DEBUG_3 endchoice endif +config BR2_ENABLE_RUNTIME_DEBUG + bool "build packages with runtime debugging info" + help + Some packages may have runtime assertions, extra traces, and + similar runtime elements that can help debugging. However, + these elements may negatively influence performance so should + normally not be enabled on production systems. + + Enable this option to enable such runtime debugging. + + Note: disabling this option is not a guarantee that all + packages effectively removed these runtime debugging elements. + config BR2_STRIP_strip bool "strip target binaries" default y -- 2.30.2