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The current IFUNC selection is based on microbenchmarks in glibc. It should give the best performance for most workloads. But other choices may have better performance for a particular workload or on the hardware which wasn't available at the selection was made. The environment variable, GLIBC_TUNABLES=glibc.tune.ifunc=-xxx,yyy,-zzz...., can be used to enable CPU/ARCH feature yyy, disable CPU/ARCH feature yyy and zzz, where the feature name is case-sensitive and has to match the ones in cpu-features.h. It can be used by glibc developers to override the IFUNC selection to tune for a new processor or improve performance for a particular workload. It isn't intended for normal end users. NOTE: the IFUNC selection may change over time. Please check all multiarch implementations when experimenting. Also, GLIBC_TUNABLES=glibc.tune.x86_non_temporal_threshold=NUMBER is provided to set threshold to use non temporal store to NUMBER, GLIBC_TUNABLES=glibc.tune.x86_data_cache_size=NUMBER to set data cache size, GLIBC_TUNABLES=glibc.tune.x86_shared_cache_size=NUMBER to set shared cache size. * elf/dl-tunables.list (tune): Add ifunc, x86_non_temporal_threshold, x86_data_cache_size and x86_shared_cache_size. * manual/tunables.texi: Document glibc.tune.ifunc, glibc.tune.x86_data_cache_size, glibc.tune.x86_shared_cache_size and glibc.tune.x86_non_temporal_threshold. * sysdeps/unix/sysv/linux/x86/dl-sysdep.c: New file. * sysdeps/x86/cpu-tunables.c: Likewise. * sysdeps/x86/cacheinfo.c (init_cacheinfo): Check and get data cache size, shared cache size and non temporal threshold from cpu_features. * sysdeps/x86/cpu-features.c [HAVE_TUNABLES] (TUNABLE_NAMESPACE): New. [HAVE_TUNABLES] Include <unistd.h>. [HAVE_TUNABLES] Include <elf/dl-tunables.h>. [HAVE_TUNABLES] (TUNABLE_CALLBACK (set_ifunc)): Likewise. [HAVE_TUNABLES] (init_cpu_features): Use TUNABLE_GET to set IFUNC selection, data cache size, shared cache size and non temporal threshold. * sysdeps/x86/cpu-features.h (cpu_features): Add data_cache_size, shared_cache_size and non_temporal_threshold. |
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| .. | ||
| bits | ||
| sys | ||
| dl-sysdep.c | ||
| elision-conf.c | ||
| elision-conf.h | ||
| elision-lock.c | ||
| elision-timed.c | ||
| elision-trylock.c | ||
| elision-unlock.c | ||
| force-elision.h | ||
| gettimeofday.c | ||
| hle.h | ||
| Implies | ||
| libc-vdso.h | ||
| Makefile | ||
| pthread_mutex_cond_lock.c | ||
| pthread_mutex_lock.c | ||
| pthread_mutex_timedlock.c | ||
| pthread_mutex_trylock.c | ||
| sysconf.c | ||
| time.c | ||