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Merge "Simplify the implementation of get_nproc()."

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Elliott Hughes 2022-07-29 18:19:29 +00:00 committed by Gerrit Code Review
commit 27b3ad2c78
2 changed files with 18 additions and 30 deletions
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44
libc/bionic/sysinfo.cpp
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@ -36,39 +36,13 @@
#include "private/get_cpu_count_from_string.h"
#include "private/ScopedReaddir.h"
static bool __matches_cpuN(const char* s) {
// The %c trick is to ensure that we have the anchored match "^cpu[0-9]+$".
// We can't use %*c because the return value is how many were *assigned*.
unsigned cpu;
char unused;
return (sscanf(s, "cpu%u%c", &cpu, &unused) == 1);
}
int get_nprocs_conf() {
// On x86 kernels you can use /proc/cpuinfo for this, but on ARM kernels offline CPUs disappear
// from there. This method works on both.
ScopedReaddir reader("/sys/devices/system/cpu");
if (reader.IsBad()) {
return 1;
}
int result = 0;
dirent* entry;
while ((entry = reader.ReadEntry()) != nullptr) {
if (entry->d_type == DT_DIR && __matches_cpuN(entry->d_name)) {
++result;
}
}
return result;
}
int get_nprocs() {
int __get_cpu_count(const char* sys_file) {
int cpu_count = 1;
FILE* fp = fopen("/sys/devices/system/cpu/online", "re");
FILE* fp = fopen(sys_file, "re");
if (fp != nullptr) {
char* line = nullptr;
size_t len = 0;
if (getline(&line, &len, fp) != -1) {
size_t allocated_size = 0;
if (getline(&line, &allocated_size, fp) != -1) {
cpu_count = GetCpuCountFromString(line);
free(line);
}
@ -77,6 +51,16 @@ int get_nprocs() {
return cpu_count;
}
int get_nprocs_conf() {
// It's unclear to me whether this is intended to be "possible" or "present",
// but on mobile they're unlikely to differ.
return __get_cpu_count("/sys/devices/system/cpu/possible");
}
int get_nprocs() {
return __get_cpu_count("/sys/devices/system/cpu/online");
}
long get_phys_pages() {
struct sysinfo si;
sysinfo(&si);

4
tests/unistd_test.cpp
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@ -1103,6 +1103,10 @@ TEST(UNISTD_TEST, get_cpu_count_from_string) {
ASSERT_EQ(4, GetCpuCountFromString("0, 1-2, 4\n"));
}
TEST(UNISTD_TEST, sysconf_SC_NPROCESSORS_make_sense) {
ASSERT_LE(sysconf(_SC_NPROCESSORS_ONLN), sysconf(_SC_NPROCESSORS_CONF));
}
TEST(UNISTD_TEST, sysconf_SC_NPROCESSORS_ONLN) {
std::string line;
ASSERT_TRUE(android::base::ReadFileToString("/sys/devices/system/cpu/online", &line));