Author: Andrew Ng Date: 2023-04-14T08:36:02+02:00 New Revision: b5aa566a7e5326e9aecf795a3fef148798092715
URL: https://github.com/llvm/llvm-project/commit/b5aa566a7e5326e9aecf795a3fef148798092715 DIFF: https://github.com/llvm/llvm-project/commit/b5aa566a7e5326e9aecf795a3fef148798092715.diff LOG: [Support] Improve Windows performance of buffered raw_ostream The "preferred" buffer size for raw_ostream is set to BUFSIZ which on Windows is only 512. This results in more calls to write and this overhead can have a significant negative impact on performance, especially when Anti-Virus is also involved. Therefore increase the "preferred" buffer size to 16KB for Windows. One example of where this helps is the LLD --Map option which dumps out the symbol map for a link. In a link of UE4, this change has been seen to improve the performance of the symbol map writing by more than a factor of 6. Differential Revision: https://reviews.llvm.org/D147340 (cherry picked from commit a3aa916d019c8deb10c750acecdef650b3365f22) Added: Modified: llvm/lib/Support/raw_ostream.cpp Removed: ################################################################################ diff --git a/llvm/lib/Support/raw_ostream.cpp b/llvm/lib/Support/raw_ostream.cpp index 7b9b8b2f53fba..fae4a4308fd7f 100644 --- a/llvm/lib/Support/raw_ostream.cpp +++ b/llvm/lib/Support/raw_ostream.cpp @@ -84,8 +84,15 @@ raw_ostream::~raw_ostream() { } size_t raw_ostream::preferred_buffer_size() const { +#ifdef _WIN32 + // On Windows BUFSIZ is only 512 which results in more calls to write. This + // overhead can cause significant performance degradation. Therefore use a + // better default. + return (16 * 1024); +#else // BUFSIZ is intended to be a reasonable default. return BUFSIZ; +#endif } void raw_ostream::SetBuffered() { _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
