Add async metrics for virtual memory mappings: VMMaxMapCount & VMNumMaps

src/Common/AsynchronousMetrics.cpp

@@ -9,6 +9,7 @@
 #include <IO/MMappedFileCache.h>
 #include <IO/ReadHelpers.h>
 #include <base/errnoToString.h>
+#include <base/find_symbols.h>
 #include <base/getPageSize.h>
 #include <sys/resource.h>
 #include <chrono>
@@ -90,6 +91,9 @@ AsynchronousMetrics::AsynchronousMetrics(
         openFileIfExists("/sys/fs/cgroup/cpu/cpu.cfs_quota_us", cgroupcpu_cfs_quota);
     }
 
+    openFileIfExists("/proc/sys/vm/max_map_count", vm_max_map_count);
+    openFileIfExists("/proc/self/maps", vm_maps);
+
     openSensors();
     openBlockDevices();
     openEDAC();
@@ -1423,6 +1427,55 @@ void AsynchronousMetrics::update(TimePoint update_time, bool force_update)
         }
     }
 
+    if (vm_max_map_count)
+    {
+        try
+        {
+            vm_max_map_count->rewind();
+
+            uint64_t max_map_count = 0;
+            readText(max_map_count, *vm_max_map_count);
+            new_values["VMMaxMapCount"] = { max_map_count, "The maximum number of memory mappings a process may have (/proc/sys/vm/max_map_count)."};
+        }
+        catch (...)
+        {
+            tryLogCurrentException(__PRETTY_FUNCTION__);
+            openFileIfExists("/proc/sys/vm/max_map_count", vm_max_map_count);
+        }
+    }
+
+    if (vm_maps)
+    {
+        try
+        {
+            vm_maps->rewind();
+
+            uint64_t num_maps = 0;
+            while (!vm_maps->eof())
+            {
+                char * next_pos = find_first_symbols<'\n'>(vm_maps->position(), vm_maps->buffer().end());
+                vm_maps->position() = next_pos;
+
+                if (!vm_maps->hasPendingData())
+                    continue;
+
+                if (*vm_maps->position() == '\n')
+                {
+                    ++num_maps;
+                    ++vm_maps->position();
+                }
+            }
+            new_values["VMNumMaps"] = { num_maps,
+                "The current number of memory mappings of the process (/proc/self/maps)."
+                " If it is close to the maximum (VMMaxMapCount), you should increase the limit for vm.max_map_count in /etc/sysctl.conf"};
+        }
+        catch (...)
+        {
+            tryLogCurrentException(__PRETTY_FUNCTION__);
+            openFileIfExists("/proc/self/maps", vm_maps);
+        }
+    }
+
     try
     {
         for (size_t i = 0, size = thermal.size(); i < size; ++i)

src/Common/AsynchronousMetrics.h

@@ -123,6 +123,9 @@ class AsynchronousMetrics
     std::optional<ReadBufferFromFilePRead> cgroupcpu_cfs_quota TSA_GUARDED_BY(data_mutex);
     std::optional<ReadBufferFromFilePRead> cgroupcpu_max TSA_GUARDED_BY(data_mutex);
 
+    std::optional<ReadBufferFromFilePRead> vm_max_map_count TSA_GUARDED_BY(data_mutex);
+    std::optional<ReadBufferFromFilePRead> vm_maps TSA_GUARDED_BY(data_mutex);
+
     std::vector<std::unique_ptr<ReadBufferFromFilePRead>> thermal TSA_GUARDED_BY(data_mutex);
 
     std::unordered_map<String /* device name */,

tests/queries/0_stateless/03010_virtual_memory_mappings_asynchronous_metrics.reference

@@ -0,0 +1,2 @@
+0
+0

tests/queries/0_stateless/03010_virtual_memory_mappings_asynchronous_metrics.sql

@@ -0,0 +1,4 @@
+-- Tags: no-replicated-database
+
+SELECT least(value, 0) FROM system.asynchronous_metrics WHERE metric = 'VMMaxMapCount';
+SELECT least(value, 0) FROM system.asynchronous_metrics WHERE metric = 'VMNumMaps';