forked from OSchip/llvm-project
e7dbebf182
Summary: In this change we introduce the notion of a "flight data recorder" mode for XRay logging, where XRay logs in-memory first, and write out data on-demand as required (as opposed to the naive implementation that keeps logging while tracing is "on"). This depends on D26232 where we implement the core data structure for holding the buffers that threads will be using to write out records of operation. This implementation only currently works on x86_64 and depends heavily on the TSC math to write out smaller records to the inmemory buffers. Also, this implementation defines two different kinds of records with different sizes (compared to the current naive implementation): a MetadataRecord (16 bytes) and a FunctionRecord (8 bytes). MetadataRecord entries are meant to write out information like the thread ID for which the metadata record is defined for, whether the execution of a thread moved to a different CPU, etc. while a FunctionRecord represents the different kinds of function call entry/exit records we might encounter in the course of a thread's execution along with a delta from the last time the logging handler was called. While this implementation is not exactly what is described in the original XRay whitepaper, this one gives us an initial implementation that we can iterate and build upon. Reviewers: echristo, rSerge, majnemer Subscribers: mehdi_amini, llvm-commits, mgorny Differential Revision: https://reviews.llvm.org/D27038 llvm-svn: 293015 |
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| sanitizer | ||
| xray | ||
| CMakeLists.txt | ||