floraachy
/
OpenBLAS
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

s390x: choose SIMD kernels at run-time based on OS and compiler support 

Extend and simplify the run-time detection for dynamic architecture support for z
to check HW_CAP and only use SIMD features if advertised by the OS.
While at it, also honor the env variable LD_HWCAP_MASK and do not use
the CPU features masked there.

Note that we can only use the SIMD features on z13 or newer (i.e.,
Vector Facility or Vector-Enhancements Facilities) when the operating
system supports properly context-switching the vector registers. The OS
advertises that support as a bit in the HW_CAP value in the auxiliary
vector. While all recent Linux kernels have that support, we should
maintain compatibility with older versions that may still be in use.

Signed-off-by: Marius Hillenbrand <mhillen@linux.ibm.com>
This commit is contained in:
Marius Hillenbrand 2020-05-11 13:00:10 +02:00
parent 62cf391cbb
commit 0dbe61a612
1 changed files with 53 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

78
driver/others/dynamic_zarch.c
View File

@ -13,6 +13,39 @@
#define HAVE_Z14_SUPPORT
#endif
// Guard the use of getauxval() on glibc version >= 2.16
#ifdef __GLIBC__
#include <features.h>
#if __GLIBC_PREREQ(2, 16)
#include <sys/auxv.h>
#define HAVE_GETAUXVAL 1
static unsigned long get_hwcap(void)
{
unsigned long hwcap = getauxval(AT_HWCAP);
char *maskenv;
// honor requests for not using specific CPU features in LD_HWCAP_MASK
maskenv = getenv("LD_HWCAP_MASK");
if (maskenv)
hwcap &= strtoul(maskenv, NULL, 0);
return hwcap;
// note that a missing auxval is interpreted as no capabilities
// available, which is safe.
}
#else // __GLIBC_PREREQ(2, 16)
#warn "Cannot detect SIMD support in Z13 or newer architectures since glibc is older than 2.16"
static unsigned long get_hwcap(void) {
// treat missing support for getauxval() as no capabilities available,
// which is safe.
return 0;
}
#endif // __GLIBC_PREREQ(2, 16)
#endif // __GLIBC
extern gotoblas_t gotoblas_ZARCH_GENERIC;
#ifdef HAVE_Z13_SUPPORT
extern gotoblas_t gotoblas_Z13;
@ -44,39 +77,34 @@ char* gotoblas_corename(void) {
return corename[0];
}
// __builtin_cpu_is is not supported by zarch
/**
* Detect the fitting set of kernels by retrieving the CPU features supported by
* OS from the auxiliary value AT_HWCAP and choosing the set of kernels
* ("coretype") that exploits most of the features and can be compiled with the
* available gcc version.
* Note that we cannot use vector registers on a z13 or newer unless supported
* by the OS kernel (which needs to handle them properly during context switch).
*/
static gotoblas_t* get_coretype(void) {
FILE* infile;
char buffer[512], * p;
p = (char*)NULL;
infile = fopen("/proc/sysinfo", "r");
while (fgets(buffer, sizeof(buffer), infile)) {
if (!strncmp("Type", buffer, 4)) {
p = strchr(buffer, ':') + 2;
#if 0
fprintf(stderr, "%s\n", p);
#endif
break;
}
}
unsigned long hwcap __attribute__((unused)) = get_hwcap();
fclose(infile);
#ifdef HAVE_Z13_SUPPORT
if (strstr(p, "2964") || strstr(p, "2965")) return &gotoblas_Z13;
#endif
// Z14 and Z15 systems
if (strstr(p, "3906") || strstr(p, "3907") || strstr(p, "8561") ||
strstr(p, "8562"))
// z14 and z15 systems: exploit Vector Facility (SIMD) and
// Vector-Enhancements Facility 1 (float SIMD instructions), if present.
#ifdef HAVE_Z14_SUPPORT
if ((hwcap & HWCAP_S390_VX) && (hwcap & HWCAP_S390_VXE))
return &gotoblas_Z14;
#else
#endif
// z13: Vector Facility (SIMD for double)
#ifdef HAVE_Z13_SUPPORT
if (hwcap & HWCAP_S390_VX)
return &gotoblas_Z13;
#endif
// unknown system or compiler too old? use generic code for z architecture
// fallback in case of missing compiler support, systems before z13, or
// when the OS does not advertise support for the Vector Facility (e.g.,
// missing support in the OS kernel)
return &gotoblas_ZARCH_GENERIC;
}