Add Linux VM dirty page settings dump at startup

Makefile.am

@@ -139,6 +139,7 @@ console_bs_SOURCES = \
     console/executor_events.cpp \
     console/executor_logging.cpp \
     console/executor_options.cpp \
+    console/executor_paging.cpp \
     console/executor_runner.cpp \
     console/executor_scans.cpp \
     console/executor_signals.cpp \

builds/msvc/vs2022/bs/bs.vcxproj

@@ -137,6 +137,7 @@
     <ClCompile Include="..\..\..\..\console\executor_events.cpp" />
     <ClCompile Include="..\..\..\..\console\executor_logging.cpp" />
     <ClCompile Include="..\..\..\..\console\executor_options.cpp" />
+    <ClCompile Include="..\..\..\..\console\executor_paging.cpp" />
     <ClCompile Include="..\..\..\..\console\executor_runner.cpp" />
     <ClCompile Include="..\..\..\..\console\executor_scans.cpp" />
     <ClCompile Include="..\..\..\..\console\executor_signals.cpp" />

builds/msvc/vs2022/bs/bs.vcxproj.filters

@@ -69,6 +69,9 @@
     <ClCompile Include="..\..\..\..\console\executor_options.cpp">
       <Filter>src</Filter>
     </ClCompile>
+    <ClCompile Include="..\..\..\..\console\executor_paging.cpp">
+      <Filter>src</Filter>
+    </ClCompile>
     <ClCompile Include="..\..\..\..\console\executor_runner.cpp">
       <Filter>src</Filter>
     </ClCompile>

console/executor.hpp

@@ -63,6 +63,7 @@ class executor
     // Store dumps.
     void dump_version() const;
     void dump_hardware() const;
+    void dump_paging() const;
     void dump_options() const;
     void dump_configuration() const;
     void dump_body_sizes() const;

console/executor_paging.cpp

@@ -0,0 +1,99 @@
+/**
+ * Copyright (c) 2011-2026 libbitcoin developers (see AUTHORS)
+ *
+ * This file is part of libbitcoin.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include "executor.hpp"
+#include "localize.hpp"
+
+#if defined(HAVE_LINUX)
+#include <charconv>
+#include <fcntl.h>
+#include <unistd.h>
+
+namespace {
+
+// Read a single decimal integer from a /proc/sys/vm sysctl entry.
+std::optional<uint64_t> read_vm_param(const char* path) noexcept
+{
+    char buffer[24]{};
+    const int fd = ::open(path, O_RDONLY);
+    if (fd < 0)
+        return std::nullopt;
+
+    const auto count = ::read(fd, buffer, sizeof(buffer) - 1u);
+    ::close(fd);
+
+    if (count <= 0)
+        return std::nullopt;
+
+    uint64_t value{};
+    const auto [ptr, ec] = std::from_chars(buffer, buffer + count, value);
+    if (ec != std::errc{})
+        return std::nullopt;
+
+    return value;
+}
+
+} // namespace
+#endif
+
+namespace libbitcoin {
+namespace server {
+
+using boost::format;
+
+// Paging dump.
+// ----------------------------------------------------------------------------
+
+void executor::dump_paging() const
+{
+#if defined(HAVE_LINUX)
+    const auto dirty_background_bytes    = read_vm_param("/proc/sys/vm/dirty_background_bytes");
+    const auto dirty_bytes               = read_vm_param("/proc/sys/vm/dirty_bytes");
+    const auto dirty_background_ratio    = read_vm_param("/proc/sys/vm/dirty_background_ratio");
+    const auto dirty_ratio               = read_vm_param("/proc/sys/vm/dirty_ratio");
+    const auto dirty_expire_centisecs    = read_vm_param("/proc/sys/vm/dirty_expire_centisecs");
+    const auto dirty_writeback_centisecs = read_vm_param("/proc/sys/vm/dirty_writeback_centisecs");
+
+    if (!dirty_background_bytes || !dirty_bytes || !dirty_background_ratio ||
+        !dirty_ratio || !dirty_expire_centisecs || !dirty_writeback_centisecs)
+        return;
+
+    const auto& log = metadata_.configured.log;
+    const auto bytes_mode = (*dirty_bytes != 0u) || (*dirty_background_bytes != 0u);
+    if (!bytes_mode)
+    {
+        if (log.dirty_ratio_minimum != 0u &&
+            *dirty_ratio >= log.dirty_ratio_minimum &&
+            log.dirty_background_ratio_minimum != 0u &&
+            *dirty_background_ratio >= log.dirty_background_ratio_minimum)
+            return;
+    }
+
+    logger(format(BS_PAGING_TABLE)
+        % (bytes_mode ? "bytes" : "ratio")
+        % *dirty_bytes
+        % *dirty_ratio
+        % *dirty_background_bytes
+        % *dirty_background_ratio
+        % *dirty_expire_centisecs
+        % *dirty_writeback_centisecs);
+#endif
+}
+
+} // namespace server
+} // namespace libbitcoin

console/executor_runner.cpp

@@ -150,6 +150,7 @@ bool executor::do_run()
     capture_.start();
     dump_version();
     dump_hardware();
+    dump_paging();
     dump_options();
     logger(BS_NODE_INTERRUPT);
 

console/localize.hpp

@@ -257,6 +257,16 @@
 #define BS_HARDWARE_TABLE2 \
     "platform:%1% compiled:%2%."
 
+#define BS_PAGING_TABLE \
+    "Linux VM dirty page kernel settings...\n" \
+    "control_mode             :%1%.\n" \
+    "dirty_bytes              :%2%.\n" \
+    "dirty_ratio              :%3%.\n" \
+    "dirty_background_bytes   :%4%.\n" \
+    "dirty_background_ratio   :%5%.\n" \
+    "dirty_expire_centisecs   :%6%.\n" \
+    "dirty_writeback_centisecs:%7%."
+
 #define BS_LOG_TABLE_HEADER \
     "Log system configuration..."
 #define BS_LOG_TABLE \

data/bs.cfg

@@ -19,6 +19,10 @@ maximum_archive_files = 0
 statistics_server = 0.0.0.0:0
 # Enable verbose logging, defaults to false.
 verbose = false
+# Warn at startup if vm.dirty_ratio is below this threshold, defaults to 90 (0 disables).
+dirty_ratio_minimum = 90
+# Warn at startup if vm.dirty_background_ratio is below this threshold, defaults to 90 (0 disables).
+dirty_background_ratio_minimum = 90
 
 [bitcoin]
 # The difficulty retargeting factor, defaults to 4.

include/bitcoin/server/settings.hpp

@@ -46,6 +46,8 @@ class BCS_API settings
     bool verbose;
 
     uint32_t maximum_size;
+    uint32_t dirty_ratio_minimum;
+    uint32_t dirty_background_ratio_minimum;
     std::filesystem::path path;
 
 #if defined (HAVE_MSC)

src/parser.cpp

@@ -1759,6 +1759,16 @@ options_metadata parser::load_settings() THROWS
         "Enable verbose logging, defaults to 'false'."
     )
 #endif
+    (
+        "log.dirty_ratio_minimum",
+        value<uint32_t>(&configured.log.dirty_ratio_minimum),
+        "Warn at startup if vm.dirty_ratio is below this threshold, defaults to 90 (0 disables)."
+    )
+    (
+        "log.dirty_background_ratio_minimum",
+        value<uint32_t>(&configured.log.dirty_background_ratio_minimum),
+        "Warn at startup if vm.dirty_background_ratio is below this threshold, defaults to 90 (0 disables)."
+    )
     (
         "log.maximum_size",
         value<uint32_t>(&configured.log.maximum_size),

src/settings.cpp

@@ -44,7 +44,9 @@ settings::settings() NOEXCEPT
     quitting{ false /*levels::quitting_defined*/ },
     objects{ false /*levels::objects_defined*/ },
     verbose{ false /*levels::verbose_defined*/ },
-    maximum_size{ 1'000'000_u32 }
+    maximum_size{ 1'000'000_u32 },
+    dirty_ratio_minimum{ 90_u32 },
+    dirty_background_ratio_minimum{ 90_u32 }
 {
 }