[PATCH] D78324: [Support][X86] Change getHostNumPhsicalCores() to return number of physical cores enabled by affinity
Fangrui Song via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Apr 16 13:23:51 PDT 2020
MaskRay created this revision.
MaskRay added reviewers: aganea, mehdi_amini, rnk, tejohnson.
Herald added subscribers: llvm-commits, hiraditya, krytarowski.
Herald added a project: LLVM.
While here, make the x86-64 code available for x86-32.
The output has been available and stable since before Linux 2.6.12-rc2 (`arch/i386/kernel/cpu/proc.c` when Linux started to use git)
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.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D78324
Files:
llvm/lib/Support/Host.cpp
Index: llvm/lib/Support/Host.cpp
===================================================================
--- llvm/lib/Support/Host.cpp
+++ llvm/lib/Support/Host.cpp
@@ -1277,13 +1277,16 @@
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() {
// Read /proc/cpuinfo as a stream (until EOF reached). It cannot be
// mmapped because it appears to have 0 size.
+ cpu_set_t Set;
+ if (sched_getaffinity(0, sizeof(Set), &Set) != 0)
+ return -1;
llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Text =
llvm::MemoryBuffer::getFileAsStream("/proc/cpuinfo");
if (std::error_code EC = Text.getError()) {
@@ -1294,28 +1297,26 @@
SmallVector<StringRef, 8> strs;
(*Text)->getBuffer().split(strs, "\n", /*MaxSplit=*/-1,
/*KeepEmpty=*/false);
+ int CurProcessor = -1;
int CurPhysicalId = -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");
+ if (Name == "processor")
+ Val.getAsInteger(10, CurProcessor);
+ else if (Name == "physical id")
Val.getAsInteger(10, CurPhysicalId);
- }
- if (Name == "core id") {
- assert(CurCoreId == -1 &&
+ else if (Name == "core id") {
+ assert((CurProcessor != -1 && CurPhysicalId != -1 && CurCoreId == -1) &&
"Expected a physical id before seeing another core id");
Val.getAsInteger(10, CurCoreId);
- }
- if (CurPhysicalId != -1 && CurCoreId != -1) {
- UniqueItems.insert(std::make_pair(CurPhysicalId, CurCoreId));
+ // The processor id corresponds to an index into cpu_set_t.
+ if (CPU_ISSET(CurProcessor, &Set))
+ UniqueItems.insert(std::make_pair(CurPhysicalId, CurCoreId));
+ CurProcessor = -1;
CurPhysicalId = -1;
CurCoreId = -1;
}
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