Dump /proc/[pid]/statm for all processes in print_mem_stats()

It can be usefull to see statm info about all processes
in the system during earlyoom killing. In some cases this
may allow tracking of "heavy" processes that haven't been killed
but are still present in system.

kill.c

@@ -18,6 +18,7 @@
 #include "kill.h"
 #include "meminfo.h"
 #include "msg.h"
+#include "utils.h"
 
 // Processes matching "--prefer REGEX" get OOM_SCORE_PREFER added to their oom_score
 #define OOM_SCORE_PREFER 300
@@ -34,25 +35,6 @@
 // At most 1 notification per second when --dryrun is active
 #define NOTIFY_RATELIMIT 1
 
-static bool isnumeric(char* str)
-{
-    int i = 0;
-
-    // Empty string is not numeric
-    if (str[0] == 0)
-        return false;
-
-    while (1) {
-        if (str[i] == 0) // End of string
-            return true;
-
-        if (isdigit(str[i]) == 0)
-            return false;
-
-        i++;
-    }
-}
-
 static void notify_dbus(const char* summary, const char* body)
 {
     int pid = fork();

meminfo.c

@@ -11,11 +11,13 @@
 #include <string.h>
 #include <sys/stat.h>
 #include <unistd.h>
+#include <dirent.h>
 
 #include "globals.h"
 #include "meminfo.h"
 #include "msg.h"
 #include "proc_pid.h"
+#include "utils.h"
 
 /* Parse the contents of /proc/meminfo (in buf), return value of "name"
  * (example: "MemTotal:")
@@ -269,6 +271,101 @@ int get_uid(int pid)
     return (int)st.st_uid;
 }
 
+static int get_process_statm(char *buf, size_t buf_size, int pid)
+{
+    char path[PATH_LEN] = { 0 };
+    snprintf(path, sizeof(path), "%s/%d/statm", procdir_path, pid);
+
+    FILE *f = fopen(path, "r");
+    if (!f) {
+        debug("%s: failed to open file '%s': %s\n", __func__, path, strerror(errno));
+        return -EINVAL;
+    }
+
+    char *res = fgets(buf, (int)buf_size, f);
+    fclose(f);
+    if (!res) {
+        debug("%s: failed to read statm info for pid=%d\n", __func__, pid);
+        return -EINVAL;
+    }
+
+    return 0;
+}
+
+static void dump_all_process_meminfo(int __attribute__((format(printf, 1, 2))) (*out_func)(const char* fmt, ...))
+{
+    DIR *procdir = opendir(procdir_path);
+    if (procdir == NULL) {
+        fatal(5, "%s: could not open /proc: %s", __func__, strerror(errno));
+    }
+
+    static size_t page_size;
+    if (page_size == 0) {
+        page_size = (size_t)sysconf(_SC_PAGESIZE);
+        if (page_size == 0) {
+            fatal(1, "could not read page size\n");
+        }
+    }
+
+    char *statm = calloc(1, page_size);
+    if (!statm) {
+        debug("%s: failed to allocate memory\n", __func__);
+        return;
+    }
+
+    out_func("===========================\n");
+    out_func("Dump all processes statm info. More details: Documentation/filesystems/proc.txt\n");
+    out_func("%%proc (%%pid): %%size %%resident %%shared %%trs %%trs %%drs %%dt\n");
+
+    while (1) {
+        errno = 0;
+        struct dirent *d = readdir(procdir);
+        if (d == NULL) {
+            if (errno != 0)
+                warn("%s: readdir error: %s\n", __func__, strerror(errno));
+            break;
+        }
+
+        // proc contains lots of directories not related to processes,
+        // skip them
+        if (!isnumeric(d->d_name))
+            continue;
+
+        errno = 0;
+        int pid = (int)strtol(d->d_name, NULL, 10);
+        if (errno != 0) {
+            warn("%s: strtol() failed: %s\n", __func__, strerror(errno));
+            continue;
+        }
+
+        // Skip kthreads
+        pid_stat_t stat;
+        if (!parse_proc_pid_stat(&stat, pid))
+            continue;
+
+        if (stat.rss <= 0)
+            continue;
+
+        int ret = get_process_statm(statm, page_size, pid);
+        if (ret < 0)
+            continue;
+
+        char name[PATH_LEN] = { 0 };
+        ret = get_comm(pid, name, sizeof(name));
+        if (ret < 0) {
+            debug("pid %d: error reading process name: %s\n", pid, strerror(-ret));
+            continue;
+        }
+
+        out_func("%s (%d): %s", name, pid, statm);
+    }
+
+    free(statm);
+    closedir(procdir);
+
+    out_func("===========================\n");
+}
+
 /* Print a status line like
  *   mem avail: 5259 MiB (67 %), swap free: 0 MiB (0 %)"
  * as an informational message to stdout (default), or
@@ -283,4 +380,6 @@ void print_mem_stats(int __attribute__((format(printf, 1, 2))) (*out_func)(const
         m.SwapFreeKiB / 1024,
         m.SwapTotalKiB / 1024,
         m.SwapFreePercent);
+
+    dump_all_process_meminfo(out_func);
 }

utils.c

@@ -0,0 +1,22 @@
+#include <ctype.h>
+
+#include "utils.h"
+
+int isnumeric(char* str)
+{
+    int i = 0;
+
+    // Empty string is not numeric
+    if (str[0] == 0)
+        return 0;
+
+    while (1) {
+        if (str[i] == 0) // End of string
+            return 1;
+
+        if (isdigit(str[i]) == 0)
+            return 0;
+
+        i++;
+    }
+}

utils.h

@@ -0,0 +1,6 @@
+#ifndef __UTILS_H__
+#define __UTILS_H__
+
+int isnumeric(char* str);
+
+#endif