Add native PCIe metrics collection and export support (#925)

* Add native PCIe metrics collection and export support

- Move IPlatform::getPlatform() from pcm-pcie.cpp to pcm-pcie.h as inline
  so both pcm-pcie (CLI) and pcm-sensor-server (HTTP exporter) can
  instantiate platform objects without duplicating the factory logic
- Add pcm-pcie-collector.h for Prometheus-style PCIe metrics collection
- Expose IPlatform data accessors (getReadBw, getWriteBw, event, etc.)
  as public so PCIeCollector can read metrics externally
- Extend pcm-sensor-server.cpp with PCIe metrics HTTP endpoints
- Replace exit() with throw std::runtime_error() for server safety
- Use override instead of virtual for compile-time correctness
- Fix build warning in pcm-pcicfg.cpp

Author: charliekang

src/pcm-pcicfg.cpp

@@ -137,7 +137,7 @@ int mainThrows(int argc, char * argv[])
         }
 
         // List all PCI devices
-        forAllDevices([&dec, &verbosity, &pciDB](const uint32 group, const uint32 bus, const uint32 device, const uint32 function, const uint32 device_id)
+        forAllDevices([&dec, &verbosity, &pciDB](const uint32 group, const uint32 bus, const uint32 device, const uint32 function, const uint32 /* device_id */)
         {
             if (PciHandleType::exists(group, bus, device, function) == false)
             {

src/pcm-pcie-collector.h

@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: BSD-3-Clause
+// Copyright (c) 2026, Intel Corporation
+#pragma once
+
+#include "pcm-pcie.h"
+
+#include <condition_variable>
+#include <mutex>
+#include <thread>
+#include <atomic>
+#include <vector>
+#include <string>
+#include <cstdint>
+#include <iostream>
+
+class PCIeCollector {
+public:
+    struct SocketBW {
+        uint64_t readBytes  = 0;
+        uint64_t writeBytes = 0;
+    };
+
+    static PCIeCollector* getInstance() {
+        static PCIeCollector instance;
+        return instance.supported_ ? &instance : nullptr;
+    }
+
+    PCIeCollector(PCIeCollector const &)            = delete;
+    PCIeCollector& operator=(PCIeCollector const &) = delete;
+    PCIeCollector(PCIeCollector &&)                 = delete;
+    PCIeCollector& operator=(PCIeCollector &&)      = delete;
+
+    static constexpr uint32_t kDefaultIntervalMs = 2000;
+
+    void startBackground(uint32_t intervalMs = kDefaultIntervalMs) {
+        bool expected = false;
+        if (!bgRunning_.compare_exchange_strong(expected, true)) return;
+        bgThread_ = std::thread([this, intervalMs]() {
+            while (bgRunning_.load()) {
+                collect();
+                std::unique_lock<std::mutex> lk(mu_);
+                cv_.wait_for(lk, std::chrono::milliseconds(intervalMs),
+                             [this] { return !bgRunning_.load(); });
+            }
+        });
+    }
+
+    void stop() {
+        bool expected = true;
+        if (!bgRunning_.compare_exchange_strong(expected, false)) return;
+        cv_.notify_one();
+        if (bgThread_.joinable()) bgThread_.join();
+    }
+
+    ~PCIeCollector() { stop(); }
+
+    uint32_t socketCount() const { return socketCount_; }
+
+    SocketBW getSocket(uint32_t skt) const {
+        std::lock_guard<std::mutex> lk(mu_);
+        if (skt < snapshot_.size()) return snapshot_[skt];
+        return {};
+    }
+
+    SocketBW getAggregate() const {
+        std::lock_guard<std::mutex> lk(mu_);
+        return aggregate_;
+    }
+
+    std::vector<uint64_t> getRawValues(uint32_t skt) const {
+        std::lock_guard<std::mutex> lk(mu_);
+        if (skt < rawValues_.size()) return rawValues_[skt];
+        return {};
+    }
+
+    std::vector<uint64_t> getRawAggregate() const {
+        std::lock_guard<std::mutex> lk(mu_);
+        return rawAggValues_;
+    }
+
+    const std::vector<std::string>& eventNames() const { return eventNames_; }
+    uint32_t numEvents() const { return static_cast<uint32_t>(eventNames_.size()); }
+    bool isSupported() const { return supported_; }
+
+private:
+    PCIeCollector() {
+        try {
+            PCM* pcm = PCM::getInstance();
+            static constexpr uint32_t kPmonMultiplier = 1000;
+            platform_.reset(IPlatform::getPlatform(pcm, false, true, false, kPmonMultiplier));
+            if (platform_) {
+                supported_ = true;
+                socketCount_ = pcm->getNumSockets();
+                const auto& names = platform_->getEventNames();
+                eventNames_.assign(names.begin(), names.end());
+                snapshot_.resize(socketCount_);
+                rawValues_.resize(socketCount_, std::vector<uint64_t>(eventNames_.size(), 0));
+                rawAggValues_.resize(eventNames_.size(), 0);
+                cumSnapshot_.resize(socketCount_);
+                cumRawValues_.resize(socketCount_, std::vector<uint64_t>(eventNames_.size(), 0));
+            }
+        } catch (const std::exception& e) {
+            std::cerr << "PCIeCollector: " << e.what() << " (PCIe metrics disabled)\n";
+            supported_ = false;
+        }
+    }
+
+    void collect() {
+        if (!platform_ || !bgRunning_.load()) return;
+        platform_->cleanup();
+        platform_->getEvents();
+
+        SocketBW aggDelta{0, 0};
+        const uint32_t nEvt = numEvents();
+
+        for (uint32_t s = 0; s < socketCount_; ++s) {
+            uint64_t dr = platform_->getReadBw(s, IPlatform::TOTAL);
+            uint64_t dw = platform_->getWriteBw(s, IPlatform::TOTAL);
+            cumSnapshot_[s].readBytes  += dr;
+            cumSnapshot_[s].writeBytes += dw;
+            aggDelta.readBytes  += dr;
+            aggDelta.writeBytes += dw;
+            for (uint32_t i = 0; i < nEvt; ++i)
+                cumRawValues_[s][i] += platform_->event(s, IPlatform::TOTAL, i);
+        }
+        cumAggregate_.readBytes  += aggDelta.readBytes;
+        cumAggregate_.writeBytes += aggDelta.writeBytes;
+
+        std::vector<uint64_t> rawAgg(nEvt, 0);
+        for (uint32_t s = 0; s < socketCount_; ++s)
+            for (uint32_t i = 0; i < nEvt; ++i)
+                rawAgg[i] += cumRawValues_[s][i];
+
+        std::lock_guard<std::mutex> lk(mu_);
+        snapshot_ = cumSnapshot_;
+        aggregate_ = cumAggregate_;
+        rawValues_ = cumRawValues_;
+        rawAggValues_ = rawAgg;
+    }
+
+    std::unique_ptr<IPlatform> platform_;
+    bool supported_ = false;
+    uint32_t socketCount_ = 0;
+    std::vector<std::string> eventNames_;
+
+    std::vector<SocketBW> snapshot_;
+    SocketBW aggregate_;
+    std::vector<std::vector<uint64_t>> rawValues_;
+    std::vector<uint64_t> rawAggValues_;
+
+    std::vector<SocketBW> cumSnapshot_;
+    SocketBW cumAggregate_;
+    std::vector<std::vector<uint64_t>> cumRawValues_;
+
+    mutable std::mutex mu_;
+    std::condition_variable cv_;
+    std::thread bgThread_;
+    std::atomic<bool> bgRunning_{false};
+};

src/pcm-pcie.cpp

@@ -93,35 +93,7 @@ void print_usage(const string & progname)
     cout << "\n";
 }
 
-IPlatform *IPlatform::getPlatform(PCM *m, bool csv, bool print_bandwidth, bool print_additional_info, uint32 delay)
-{
-    switch (m->getCPUFamilyModel()) {
-        case PCM::GNR:
-        case PCM::GNR_D:
-        case PCM::SRF:
-            return new BirchStreamPlatform(m, csv, print_bandwidth, print_additional_info, delay);
-        case PCM::GRR:
-            return new LoganvillePlatform(m, csv, print_bandwidth, print_additional_info, delay);
-        case PCM::SPR:
-        case PCM::EMR:
-            return new EagleStreamPlatform(m, csv, print_bandwidth, print_additional_info, delay);
-        case PCM::ICX:
-        case PCM::SNOWRIDGE:
-            return new WhitleyPlatform(m, csv, print_bandwidth, print_additional_info, delay);
-        case PCM::SKX:
-            return new PurleyPlatform(m, csv, print_bandwidth, print_additional_info, delay);
-        case PCM::BDX_DE:
-        case PCM::BDX:
-        case PCM::KNL:
-        case PCM::HASWELLX:
-            return new GrantleyPlatform(m, csv, print_bandwidth, print_additional_info, delay);
-        case PCM::IVYTOWN:
-        case PCM::JAKETOWN:
-            return new BromolowPlatform(m, csv, print_bandwidth, print_additional_info, delay);
-        default:
-          return NULL;
-    }
-}
+// getPlatform() is defined inline in pcm-pcie.h.
 
 PCM_MAIN_NOTHROW;