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[Support][X86] Change getHostNumPhsicalCores() to return number of physical cores enabled by affinity

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Fixes https://bugs.llvm.org/show_bug.cgi?id=45556

While here, make the x86-64 code available for x86-32.

The output has been available and stable since
https://git.kernel.org/linus/3dd9d514846cdca1dcef2e4fce666d85e199e844 (2005)
```
processor:
...
physical id:
siblings:
core id:
```

Don't check HAVE_SCHED_GETAFFINITY/HAVE_CPU_COUNT. The interface is
simply available in every libc which can build LLVM.

Reviewed By: aganea

Differential Revision: https://reviews.llvm.org/D78324
This commit is contained in:
Fangrui Song 2020-04-16 12:05:53 -07:00
parent a86090197b
commit fbe84ef7cc
1 changed files with 22 additions and 19 deletions
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41
lib/Support/Host.cpp
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@ -1277,11 +1277,18 @@ StringRef sys::getHostCPUName() {
StringRef sys::getHostCPUName() { return "generic"; }
#endif
#if defined(__linux__) && defined(__x86_64__)
#if defined(__linux__) && (defined(__i386__) || defined(__x86_64__))
// On Linux, the number of physical cores can be computed from /proc/cpuinfo,
// using the number of unique physical/core id pairs. The following
// implementation reads the /proc/cpuinfo format on an x86_64 system.
int computeHostNumPhysicalCores() {
// Enabled represents the number of physical id/core id pairs with at least
// one processor id enabled by the CPU affinity mask.
cpu_set_t Affinity, Enabled;
if (sched_getaffinity(0, sizeof(Affinity), &Affinity) != 0)
return -1;
CPU_ZERO(&Enabled);
// Read /proc/cpuinfo as a stream (until EOF reached). It cannot be
// mmapped because it appears to have 0 size.
llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Text =
@ -1294,33 +1301,29 @@ int computeHostNumPhysicalCores() {
SmallVector<StringRef, 8> strs;
(*Text)->getBuffer().split(strs, "\n", /*MaxSplit=*/-1,
/*KeepEmpty=*/false);
int CurProcessor = -1;
int CurPhysicalId = -1;
int CurSiblings = -1;
int CurCoreId = -1;
SmallSet<std::pair<int, int>, 32> UniqueItems;
for (auto &Line : strs) {
Line = Line.trim();
if (!Line.startswith("physical id") && !Line.startswith("core id"))
continue;
for (StringRef Line : strs) {
std::pair<StringRef, StringRef> Data = Line.split(':');
auto Name = Data.first.trim();
auto Val = Data.second.trim();
if (Name == "physical id") {
assert(CurPhysicalId == -1 &&
"Expected a core id before seeing another physical id");
// These fields are available if the kernel is configured with CONFIG_SMP.
if (Name == "processor")
Val.getAsInteger(10, CurProcessor);
else if (Name == "physical id")
Val.getAsInteger(10, CurPhysicalId);
}
if (Name == "core id") {
assert(CurCoreId == -1 &&
"Expected a physical id before seeing another core id");
else if (Name == "siblings")
Val.getAsInteger(10, CurSiblings);
else if (Name == "core id") {
Val.getAsInteger(10, CurCoreId);
}
if (CurPhysicalId != -1 && CurCoreId != -1) {
UniqueItems.insert(std::make_pair(CurPhysicalId, CurCoreId));
CurPhysicalId = -1;
CurCoreId = -1;
// The processor id corresponds to an index into cpu_set_t.
if (CPU_ISSET(CurProcessor, &Affinity))
CPU_SET(CurPhysicalId * CurSiblings + CurCoreId, &Enabled);
}
}
return UniqueItems.size();
return CPU_COUNT(&Enabled);
}
#elif defined(__APPLE__) && defined(__x86_64__)
#include <sys/param.h>