Replace get_vm_rss_kib with parse_proc_pid_stat and delete it

It's slower, but we get the ppid from it, which we will need
for detecting kernel threads.

Benchmark_get_vm_rss_kib-4         	  178054	      6920 ns/op
Benchmark_parse_proc_pid_stat-4    	  107766	     11614 ns/op

kill.c

@@ -296,12 +296,13 @@ bool is_larger(const poll_loop_args_t* args, const procinfo_t* victim, procinfo_
     }
 
     {
-        long long res = get_vm_rss_kib(cur->pid);
-        if (res < 0) {
-            debug("%s: pid %d: error reading rss: %s\n", __func__, cur->pid, strerror((int)-res));
+        bool res = parse_proc_pid_stat(&cur->stat, cur->pid);
+        if (!res) {
+            debug("%s: pid %d: error reading stat\n", __func__, cur->pid);
             return false;
         }
-        cur->VmRSSkiB = res;
+        const long page_size = sysconf(_SC_PAGESIZE);
+        cur->VmRSSkiB = cur->stat.rss * page_size / 1024;
     }
 
     if ((args->prefer_regex || args->avoid_regex || args->ignore_regex)) {

meminfo.c

@@ -269,39 +269,6 @@ int get_uid(int pid)
     return (int)st.st_uid;
 }
 
-// Read VmRSS from /proc/[pid]/statm and convert to kiB.
-// Returns the value (>= 0) or -errno on error.
-long long get_vm_rss_kib(int pid)
-{
-    long long vm_rss_kib = -1;
-    char path[PATH_LEN] = { 0 };
-
-    // Read VmRSS from /proc/[pid]/statm (in pages)
-    snprintf(path, sizeof(path), "%s/%d/statm", procdir_path, pid);
-    FILE* f = fopen(path, "r");
-    if (f == NULL) {
-        return -errno;
-    }
-    int matches = fscanf(f, "%*u %lld", &vm_rss_kib);
-    fclose(f);
-    if (matches < 1) {
-        return -ENODATA;
-    }
-
-    // Read and cache page size
-    static long page_size;
-    if (page_size == 0) {
-        page_size = sysconf(_SC_PAGESIZE);
-        if (page_size <= 0) {
-            fatal(1, "could not read page size\n");
-        }
-    }
-
-    // Convert to kiB
-    vm_rss_kib = vm_rss_kib * page_size / 1024;
-    return vm_rss_kib;
-}
-
 /* Print a status line like
  *   mem avail: 5259 MiB (67 %), swap free: 0 MiB (0 %)"
  * as an informational message to stdout (default), or

meminfo.h

@@ -5,6 +5,7 @@
 #define PATH_LEN 256
 
 #include <stdbool.h>
+#include "proc_pid.h"
 
 typedef struct {
     // Values from /proc/meminfo, in KiB
@@ -28,6 +29,7 @@ typedef struct procinfo {
     int badness;
     int oom_score_adj;
     long long VmRSSkiB;
+    pid_stat_t stat;
     char name[PATH_LEN];
     char cmdline[PATH_LEN];
 } procinfo_t;
@@ -37,7 +39,6 @@ bool is_alive(int pid);
 void print_mem_stats(int (*out_func)(const char* fmt, ...), const meminfo_t m);
 int get_oom_score(int pid);
 int get_oom_score_adj(const int pid, int* out);
-long long get_vm_rss_kib(int pid);
 int get_comm(int pid, char* out, size_t outlen);
 int get_uid(int pid);
 int get_cmdline(int pid, char* out, size_t outlen);

testsuite_c_wrappers.go

@@ -94,10 +94,6 @@ func get_oom_score_adj(pid int, out *int) int {
 	return int(res)
 }
 
-func get_vm_rss_kib(pid int) int {
-	return int(C.get_vm_rss_kib(C.int(pid)))
-}
-
 func get_comm(pid int) (int, string) {
 	cstr := C.CString(strings.Repeat("\000", 256))
 	res := C.get_comm(C.int(pid), cstr, 256)

testsuite_helpers.go

@@ -11,6 +11,8 @@ import (
 	"syscall"
 	"testing"
 	"time"
+
+	linuxproc "github.com/c9s/goprocinfo/linux"
 )
 
 // #include "meminfo.h"
@@ -84,7 +86,12 @@ func runEarlyoom(t *testing.T, args ...string) exitVals {
 		}
 	}
 	timer.Stop()
-	rss := get_vm_rss_kib(cmd.Process.Pid)
+
+	stat, err := linuxproc.ReadProcessStat(fmt.Sprintf("/proc/%d/stat", cmd.Process.Pid))
+	if err != nil {
+		panic(err)
+	}
+	rss := int(stat.Rss)
 	fds := countFds(cmd.Process.Pid)
 	cmd.Process.Kill()
 	err = cmd.Wait()
@@ -199,8 +206,8 @@ func mockProc(t *testing.T, procs []mockProcProcess) {
 		// stat
 		//
 		// Real /proc/pid/stat string for gnome-shell
-		template := "549077 (%s) S 547891 549077 549077 0 -1 4194560 245592 104 342 5 108521 28953 0 1 20 0 %d 0 4816953 5260238848 65528 18446744073709551615 94179647238144 94179647245825 140730757359824 0 0 0 0 16781312 17656 0 0 0 17 1 0 0 0 0 0 94179647252976 94179647254904 94179672109056 140730757367876 140730757367897 140730757367897 140730757369827 0\n"
-		content = []byte(fmt.Sprintf(template, p.comm, p.num_threads))
+		template := "549077 (%s) S 547891 549077 549077 0 -1 4194560 245592 104 342 5 108521 28953 0 1 20 0 %d 0 4816953 5260238848 %d 18446744073709551615 94179647238144 94179647245825 140730757359824 0 0 0 0 16781312 17656 0 0 0 17 1 0 0 0 0 0 94179647252976 94179647254904 94179672109056 140730757367876 140730757367897 140730757367897 140730757369827 0\n"
+		content = []byte(fmt.Sprintf(template, p.comm, p.num_threads, rss))
 		if err := ioutil.WriteFile(pidDir+"/stat", content, 0444); err != nil {
 			t.Fatal(err)
 		}

testsuite_unit_test.go

@@ -148,19 +148,6 @@ func Test_fix_truncated_utf8(t *testing.T) {
 	}
 }
 
-func Test_get_vm_rss_kib(t *testing.T) {
-	pid := os.Getpid()
-	rss := get_vm_rss_kib(pid)
-	if rss <= 0 {
-		t.Fatalf("our rss can't be <= 0, but we got %d", rss)
-	}
-	// Error case
-	res := get_vm_rss_kib(INT32_MAX)
-	if res != -ENOENT {
-		t.Fail()
-	}
-}
-
 func Test_get_oom_score(t *testing.T) {
 	res := get_oom_score(os.Getpid())
 	// On systems with a lot of RAM, our process may actually have a score of
@@ -389,33 +376,6 @@ func Benchmark_get_oom_score_adj(b *testing.B) {
 	}
 }
 
-func Benchmark_get_vm_rss_kib(b *testing.B) {
-	enable_debug(false)
-
-	pid := os.Getpid()
-	for n := 0; n < b.N; n++ {
-		rss := get_vm_rss_kib(pid)
-		if rss <= 0 {
-			b.Fatalf("rss <= 0: %d", rss)
-		}
-	}
-}
-
-func Benchmark_get_comm(b *testing.B) {
-	enable_debug(false)
-
-	pid := os.Getpid()
-	for n := 0; n < b.N; n++ {
-		res, comm := get_comm(pid)
-		if len(comm) == 0 {
-			b.Fatalf("empty process name %q", comm)
-		}
-		if res != 0 {
-			b.Fatalf("error %d", res)
-		}
-	}
-}
-
 func Benchmark_get_cmdline(b *testing.B) {
 	enable_debug(false)