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| author | Wilco Dijkstra <wilco.dijkstra@arm.com> | 2024-03-21 16:48:33 +0000 |
|---|---|---|
| committer | Wilco Dijkstra <wilco.dijkstra@arm.com> | 2024-03-21 16:50:51 +0000 |
| commit | 2e94e2f5d2bf2de124c8ad7da85463355e54ccb2 (patch) | |
| tree | 984e784ebbfb84f3a82fd0c7f1604000289b577f /sysdeps/aarch64 | |
| parent | 1ea051145612f199d8716ecdf78b084b00b5a727 (diff) | |
| download | glibc-2e94e2f5d2bf2de124c8ad7da85463355e54ccb2.tar.xz glibc-2e94e2f5d2bf2de124c8ad7da85463355e54ccb2.zip | |
AArch64: Check kernel version for SVE ifuncs
Old Linux kernels disable SVE after every system call. Calling the
SVE-optimized memcpy afterwards will then cause a trap to reenable SVE.
As a result, applications with a high use of syscalls may run slower with
the SVE memcpy. This is true for kernels between 4.15.0 and before 6.2.0,
except for 5.14.0 which was patched. Avoid this by checking the kernel
version and selecting the SVE ifunc on modern kernels.
Parse the kernel version reported by uname() into a 24-bit kernel.major.minor
value without calling any library functions. If uname() is not supported or
if the version format is not recognized, assume the kernel is modern.
Tested-by: Florian Weimer <fweimer@redhat.com>
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
Diffstat (limited to 'sysdeps/aarch64')
| -rw-r--r-- | sysdeps/aarch64/cpu-features.h | 1 | ||||
| -rw-r--r-- | sysdeps/aarch64/multiarch/init-arch.h | 2 | ||||
| -rw-r--r-- | sysdeps/aarch64/multiarch/memcpy.c | 2 | ||||
| -rw-r--r-- | sysdeps/aarch64/multiarch/memmove.c | 2 |
4 files changed, 5 insertions, 2 deletions
diff --git a/sysdeps/aarch64/cpu-features.h b/sysdeps/aarch64/cpu-features.h index 77a782422a..5f2da91ebb 100644 --- a/sysdeps/aarch64/cpu-features.h +++ b/sysdeps/aarch64/cpu-features.h @@ -71,6 +71,7 @@ struct cpu_features /* Currently, the GLIBC memory tagging tunable only defines 8 bits. */ uint8_t mte_state; bool sve; + bool prefer_sve_ifuncs; bool mops; }; diff --git a/sysdeps/aarch64/multiarch/init-arch.h b/sysdeps/aarch64/multiarch/init-arch.h index c52860efb2..61dc40088f 100644 --- a/sysdeps/aarch64/multiarch/init-arch.h +++ b/sysdeps/aarch64/multiarch/init-arch.h @@ -36,5 +36,7 @@ MTE_ENABLED (); \ bool __attribute__((unused)) sve = \ GLRO(dl_aarch64_cpu_features).sve; \ + bool __attribute__((unused)) prefer_sve_ifuncs = \ + GLRO(dl_aarch64_cpu_features).prefer_sve_ifuncs; \ bool __attribute__((unused)) mops = \ GLRO(dl_aarch64_cpu_features).mops; diff --git a/sysdeps/aarch64/multiarch/memcpy.c b/sysdeps/aarch64/multiarch/memcpy.c index d12eccfca5..ce53567dab 100644 --- a/sysdeps/aarch64/multiarch/memcpy.c +++ b/sysdeps/aarch64/multiarch/memcpy.c @@ -47,7 +47,7 @@ select_memcpy_ifunc (void) { if (IS_A64FX (midr)) return __memcpy_a64fx; - return __memcpy_sve; + return prefer_sve_ifuncs ? __memcpy_sve : __memcpy_generic; } if (IS_THUNDERX (midr)) diff --git a/sysdeps/aarch64/multiarch/memmove.c b/sysdeps/aarch64/multiarch/memmove.c index 2081eeb4d4..fe95037be3 100644 --- a/sysdeps/aarch64/multiarch/memmove.c +++ b/sysdeps/aarch64/multiarch/memmove.c @@ -47,7 +47,7 @@ select_memmove_ifunc (void) { if (IS_A64FX (midr)) return __memmove_a64fx; - return __memmove_sve; + return prefer_sve_ifuncs ? __memmove_sve : __memmove_generic; } if (IS_THUNDERX (midr)) |