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Previously we use `rep stosb` for all medium/large memsets. This is notably worse than non-temporal stores for large (above a few MBs) memsets. See: https://docs.google.com/spreadsheets/d/1opzukzvum4n6-RUVHTGddV6RjAEil4P2uMjjQGLbLcU/edit?usp=sharing For data using different stategies for large memset on ICX and SKX. Using non-temporal stores can be up to 3x faster on ICX and 2x faster on SKX. Historically, these numbers would not have been so good because of the zero-over-zero writeback optimization that `rep stosb` is able to do. But, the zero-over-zero writeback optimization has been removed as a potential side-channel attack, so there is no longer any good reason to only rely on `rep stosb` for large memsets. On the flip size, non-temporal writes can avoid data in their RFO requests saving memory bandwidth. All of the other changes to the file are to re-organize the code-blocks to maintain "good" alignment given the new code added in the `L(stosb_local)` case. The results from running the GLIBC memset benchmarks on TGL-client for N=20 runs: Geometric Mean across the suite New / Old EXEX256: 0.979 Geometric Mean across the suite New / Old EXEX512: 0.979 Geometric Mean across the suite New / Old AVX2 : 0.986 Geometric Mean across the suite New / Old SSE2 : 0.979 Most of the cases are essentially unchanged, this is mostly to show that adding the non-temporal case didn't add any regressions to the other cases. The results on the memset-large benchmark suite on TGL-client for N=20 runs: Geometric Mean across the suite New / Old EXEX256: 0.926 Geometric Mean across the suite New / Old EXEX512: 0.925 Geometric Mean across the suite New / Old AVX2 : 0.928 Geometric Mean across the suite New / Old SSE2 : 0.924 So roughly a 7.5% speedup. This is lower than what we see on servers (likely because clients typically have faster single-core bandwidth so saving bandwidth on RFOs is less impactful), but still advantageous. Full test-suite passes on x86_64 w/ and w/o multiarch. Reviewed-by: H.J. Lu <hjl.tools@gmail.com> |
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This directory contains the sources of the GNU C Library. See the file "version.h" for what release version you have. The GNU C Library is the standard system C library for all GNU systems, and is an important part of what makes up a GNU system. It provides the system API for all programs written in C and C-compatible languages such as C++ and Objective C; the runtime facilities of other programming languages use the C library to access the underlying operating system. In GNU/Linux systems, the C library works with the Linux kernel to implement the operating system behavior seen by user applications. In GNU/Hurd systems, it works with a microkernel and Hurd servers. The GNU C Library implements much of the POSIX.1 functionality in the GNU/Hurd system, using configurations i[4567]86-*-gnu and x86_64-gnu. When working with Linux kernels, this version of the GNU C Library requires Linux kernel version 3.2 or later. Also note that the shared version of the libgcc_s library must be installed for the pthread library to work correctly. The GNU C Library supports these configurations for using Linux kernels: aarch64*-*-linux-gnu alpha*-*-linux-gnu arc*-*-linux-gnu arm-*-linux-gnueabi csky-*-linux-gnuabiv2 hppa-*-linux-gnu i[4567]86-*-linux-gnu x86_64-*-linux-gnu Can build either x86_64 or x32 loongarch64-*-linux-gnu Hardware floating point, LE only. m68k-*-linux-gnu microblaze*-*-linux-gnu mips-*-linux-gnu mips64-*-linux-gnu or1k-*-linux-gnu powerpc-*-linux-gnu Hardware or software floating point, BE only. powerpc64*-*-linux-gnu Big-endian and little-endian. s390-*-linux-gnu s390x-*-linux-gnu riscv32-*-linux-gnu riscv64-*-linux-gnu sh[34]-*-linux-gnu sparc*-*-linux-gnu sparc64*-*-linux-gnu If you are interested in doing a port, please contact the glibc maintainers; see https://www.gnu.org/software/libc/ for more information. See the file INSTALL to find out how to configure, build, and install the GNU C Library. You might also consider reading the WWW pages for the C library at https://www.gnu.org/software/libc/. The GNU C Library is (almost) completely documented by the Texinfo manual found in the `manual/' subdirectory. The manual is still being updated and contains some known errors and omissions; we regret that we do not have the resources to work on the manual as much as we would like. For corrections to the manual, please file a bug in the `manual' component, following the bug-reporting instructions below. Please be sure to check the manual in the current development sources to see if your problem has already been corrected. Please see https://www.gnu.org/software/libc/bugs.html for bug reporting information. We are now using the Bugzilla system to track all bug reports. This web page gives detailed information on how to report bugs properly. The GNU C Library is free software. See the file COPYING.LIB for copying conditions, and LICENSES for notices about a few contributions that require these additional notices to be distributed. License copyright years may be listed using range notation, e.g., 1996-2015, indicating that every year in the range, inclusive, is a copyrightable year that would otherwise be listed individually.