mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-11 22:00:08 +00:00
ea69248445
When mutiple threads waiting for lock at the same time, once lock owner
releases the lock, waiters will see lock available and all try to lock,
which may cause an expensive CAS storm.
Binary exponential backoff with random jitter is introduced. As try-lock
attempt increases, there is more likely that a larger number threads
compete for adaptive mutex lock, so increase wait time in exponential.
A random jitter is also added to avoid synchronous try-lock from other
threads.
v2: Remove read-check before try-lock for performance.
v3:
1. Restore read-check since it works well in some platform.
2. Make backoff arch dependent, and enable it for x86_64.
3. Limit max backoff to reduce latency in large critical section.
v4: Fix strict-prototypes error in sysdeps/nptl/pthread_mutex_backoff.h
v5: Commit log updated for regression in large critical section.
Result of pthread-mutex-locks bench
Test Platform: Xeon 8280L (2 socket, 112 CPUs in total)
First Row: thread number
First Col: critical section length
Values: backoff vs upstream, time based, low is better
non-critical-length: 1
1 2 4 8 16 32 64 112 140
0 0.99 0.58 0.52 0.49 0.43 0.44 0.46 0.52 0.54
1 0.98 0.43 0.56 0.50 0.44 0.45 0.50 0.56 0.57
2 0.99 0.41 0.57 0.51 0.45 0.47 0.48 0.60 0.61
4 0.99 0.45 0.59 0.53 0.48 0.49 0.52 0.64 0.65
8 1.00 0.66 0.71 0.63 0.56 0.59 0.66 0.72 0.71
16 0.97 0.78 0.91 0.73 0.67 0.70 0.79 0.80 0.80
32 0.95 1.17 0.98 0.87 0.82 0.86 0.89 0.90 0.90
64 0.96 0.95 1.01 1.01 0.98 1.00 1.03 0.99 0.99
128 0.99 1.01 1.01 1.17 1.08 1.12 1.02 0.97 1.02
non-critical-length: 32
1 2 4 8 16 32 64 112 140
0 1.03 0.97 0.75 0.65 0.58 0.58 0.56 0.70 0.70
1 0.94 0.95 0.76 0.65 0.58 0.58 0.61 0.71 0.72
2 0.97 0.96 0.77 0.66 0.58 0.59 0.62 0.74 0.74
4 0.99 0.96 0.78 0.66 0.60 0.61 0.66 0.76 0.77
8 0.99 0.99 0.84 0.70 0.64 0.66 0.71 0.80 0.80
16 0.98 0.97 0.95 0.76 0.70 0.73 0.81 0.85 0.84
32 1.04 1.12 1.04 0.89 0.82 0.86 0.93 0.91 0.91
64 0.99 1.15 1.07 1.00 0.99 1.01 1.05 0.99 0.99
128 1.00 1.21 1.20 1.22 1.25 1.31 1.12 1.10 0.99
non-critical-length: 128
1 2 4 8 16 32 64 112 140
0 1.02 1.00 0.99 0.67 0.61 0.61 0.61 0.74 0.73
1 0.95 0.99 1.00 0.68 0.61 0.60 0.60 0.74 0.74
2 1.00 1.04 1.00 0.68 0.59 0.61 0.65 0.76 0.76
4 1.00 0.96 0.98 0.70 0.63 0.63 0.67 0.78 0.77
8 1.01 1.02 0.89 0.73 0.65 0.67 0.71 0.81 0.80
16 0.99 0.96 0.96 0.79 0.71 0.73 0.80 0.84 0.84
32 0.99 0.95 1.05 0.89 0.84 0.85 0.94 0.92 0.91
64 1.00 0.99 1.16 1.04 1.00 1.02 1.06 0.99 0.99
128 1.00 1.06 0.98 1.14 1.39 1.26 1.08 1.02 0.98
There is regression in large critical section. But adaptive mutex is
aimed for "quick" locks. Small critical section is more common when
users choose to use adaptive pthread_mutex.
Signed-off-by: Wangyang Guo <wangyang.guo@intel.com>
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
(cherry picked from commit
|
||
|---|---|---|
| argp | ||
| assert | ||
| benchtests | ||
| bits | ||
| catgets | ||
| ChangeLog.old | ||
| conform | ||
| crypt | ||
| csu | ||
| ctype | ||
| debug | ||
| dirent | ||
| dlfcn | ||
| elf | ||
| gmon | ||
| gnulib | ||
| grp | ||
| gshadow | ||
| hesiod | ||
| htl | ||
| hurd | ||
| iconv | ||
| iconvdata | ||
| include | ||
| inet | ||
| intl | ||
| io | ||
| libio | ||
| locale | ||
| localedata | ||
| login | ||
| mach | ||
| malloc | ||
| manual | ||
| math | ||
| mathvec | ||
| misc | ||
| nis | ||
| nptl | ||
| nptl_db | ||
| nscd | ||
| nss | ||
| po | ||
| posix | ||
| pwd | ||
| resolv | ||
| resource | ||
| rt | ||
| scripts | ||
| setjmp | ||
| shadow | ||
| signal | ||
| socket | ||
| soft-fp | ||
| stdio-common | ||
| stdlib | ||
| string | ||
| sunrpc | ||
| support | ||
| sysdeps | ||
| sysvipc | ||
| termios | ||
| time | ||
| timezone | ||
| wcsmbs | ||
| wctype | ||
| .gitattributes | ||
| .gitignore | ||
| abi-tags | ||
| aclocal.m4 | ||
| config.h.in | ||
| config.make.in | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
| COPYING.LIB | ||
| extra-lib.mk | ||
| gen-locales.mk | ||
| INSTALL | ||
| libc-abis | ||
| libof-iterator.mk | ||
| LICENSES | ||
| MAINTAINERS | ||
| Makeconfig | ||
| Makefile | ||
| Makefile.help | ||
| Makefile.in | ||
| Makerules | ||
| NEWS | ||
| o-iterator.mk | ||
| README | ||
| Rules | ||
| shlib-versions | ||
| test-skeleton.c | ||
| version.h | ||
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. 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 ia64-*-linux-gnu m68k-*-linux-gnu microblaze*-*-linux-gnu mips-*-linux-gnu mips64-*-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.