1 files changed, 74 insertions, 0 deletions
diff --git a/collectors/systemd-journal.plugin/systemd-journal-fstat.c b/collectors/systemd-journal.plugin/systemd-journal-fstat.c
new file mode 100644
index 00000000..45ea7817
--- /dev/null
+++ b/collectors/systemd-journal.plugin/systemd-journal-fstat.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "systemd-internals.h"
+
+
+// ----------------------------------------------------------------------------
+// fstat64 overloading to speed up libsystemd
+// https://github.com/systemd/systemd/pull/29261
+
+#include <dlfcn.h>
+#include <sys/stat.h>
+
+#define FSTAT_CACHE_MAX 1024
+struct fdstat64_cache_entry {
+    bool enabled;
+    bool updated;
+    int err_no;
+    struct stat64 stat;
+    int ret;
+    size_t cached_count;
+    size_t session;
+};
+
+struct fdstat64_cache_entry fstat64_cache[FSTAT_CACHE_MAX] = {0 };
+__thread size_t fstat_thread_calls = 0;
+__thread size_t fstat_thread_cached_responses = 0;
+static __thread bool enable_thread_fstat = false;
+static __thread size_t fstat_caching_thread_session = 0;
+static size_t fstat_caching_global_session = 0;
+
+void fstat_cache_enable_on_thread(void) {
+    fstat_caching_thread_session = __atomic_add_fetch(&fstat_caching_global_session, 1, __ATOMIC_ACQUIRE);
+    enable_thread_fstat = true;
+}
+
+void fstat_cache_disable_on_thread(void) {
+    fstat_caching_thread_session = __atomic_add_fetch(&fstat_caching_global_session, 1, __ATOMIC_RELEASE);
+    enable_thread_fstat = false;
+}
+
+int fstat64(int fd, struct stat64 *buf) {
+    static int (*real_fstat)(int, struct stat64 *) = NULL;
+    if (!real_fstat)
+        real_fstat = dlsym(RTLD_NEXT, "fstat64");
+
+    fstat_thread_calls++;
+
+    if(fd >= 0 && fd < FSTAT_CACHE_MAX) {
+        if(enable_thread_fstat && fstat64_cache[fd].session != fstat_caching_thread_session) {
+            fstat64_cache[fd].session = fstat_caching_thread_session;
+            fstat64_cache[fd].enabled = true;
+            fstat64_cache[fd].updated = false;
+        }
+
+        if(fstat64_cache[fd].enabled && fstat64_cache[fd].updated && fstat64_cache[fd].session == fstat_caching_thread_session) {
+            fstat_thread_cached_responses++;
+            errno = fstat64_cache[fd].err_no;
+            *buf = fstat64_cache[fd].stat;
+            fstat64_cache[fd].cached_count++;
+            return fstat64_cache[fd].ret;
+        }
+    }
+
+    int ret = real_fstat(fd, buf);
+
+    if(fd >= 0 && fd < FSTAT_CACHE_MAX && fstat64_cache[fd].enabled && fstat64_cache[fd].session == fstat_caching_thread_session) {
+        fstat64_cache[fd].ret = ret;
+        fstat64_cache[fd].updated = true;
+        fstat64_cache[fd].err_no = errno;
+        fstat64_cache[fd].stat = *buf;
+    }
+
+    return ret;
+}