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Rollback f040e96b93

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PiperOrigin-RevId: 802588083
Change-Id: Ibea44bd227dda2f4ebc7e24890426faa7a83b36b
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Abseil Team
2025-09-03 09:33:46 -07:00
committed by Copybara-Service
parent 79bdf3b41f
commit 9dc9586eff
1 changed files with 0 additions and 65 deletions
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65
absl/base/internal/sysinfo.cc
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@@ -135,69 +135,6 @@ int Win32NumCPUs() {
#endif
#if defined(__linux__)
// Kinda like perror, but without allocating. At least, mostly...
void PerrorNoAlloc(const char* msg) {
// strerror might allocate, theoretically. In practice, it doesn't do so on
// glibc unless you provide an invalid errno, and never allocates on musl.
char *errmsg = strerror(errno);
// snprintf isn't technically on the async-signal-safe list, but, in practice,
// it doesn't allocate.
char buf[1024];
int len = snprintf(buf, sizeof(buf), "%s: %s\n", msg, errmsg);
if (len > 0) {
if ((unsigned)len > sizeof(buf)) len = sizeof(buf);
ABSL_ATTRIBUTE_UNUSED auto ret = write(2, buf, static_cast<size_t>(len));
}
}
// Returns the number of possible cpus by parsing a sysfs string.
int ParseSysFsPossibleCPUs(const char* str, size_t len) {
if (len == 0) return 1;
// Find the last number in the line and parse that -- that'll be the highest
// cpu number.
for (int i = static_cast<int>(len - 1); i >= 0; --i) {
if (!isdigit(str[i])) return atoi(&str[i+1]) + 1; // NOLINT
}
return atoi(str) + 1; // NOLINT
}
int GetNumPossibleCpusFromSysfs() {
// The "possible" file exists since Linux 2.6.26.
//
// It contains a value such as "0-127" (meaning you have 128 CPUs, numbered 0
// through 127). The format used here also supports strings like: "0,2,4-7" to
// describe discontiguous ids, but that cannot actually happen here, since
// "possible" CPU numbers are always contiguous from 0 to the maximum.
int fd;
do {
fd = open("/sys/devices/system/cpu/possible", O_RDONLY | O_CLOEXEC);
} while (fd < 0 && errno == EINTR);
if (fd < 0) {
PerrorNoAlloc("GetNumPossibleCpusFromSysfs: open() failed");
abort();
}
char buf[1024];
ssize_t len;
do {
len = read(fd, buf, sizeof(buf) - 1);
} while (len < 0 && errno == EINTR);
if (len <= 0) {
PerrorNoAlloc("GetNumPossibleCpusFromSysfs: read() failed");
abort();
}
close(fd);
if (buf[len - 1] == '\n') --len;
buf[len] = '\0';
return ParseSysFsPossibleCPUs(buf, static_cast<size_t>(len));
}
#endif
} // namespace
static int GetNumCPUs() {
@@ -208,8 +145,6 @@ static int GetNumCPUs() {
return hardware_concurrency ? hardware_concurrency : 1;
#elif defined(_AIX)
return sysconf(_SC_NPROCESSORS_ONLN);
#elif defined(__linux__)
return GetNumPossibleCpusFromSysfs();
#else
// Other possibilities:
// - Read /sys/devices/system/cpu/online and use cpumask_parse()