Fix last COW INFO report, Skip test on non-linux platforms (#8301)

- the last COW report wasn't always read from the pipe
  (receiveLastChildInfo wasn't used)
- but in fact, there's no reason we won't always try to drain that pipe
  so i'm unifying receiveLastChildInfo with receiveChildInfo
- adjust threshold of the COW test when run in accurate mode
- add some prints in case this test fails again
- fix indentation, page size, and PID! in MacOS proc info

p.s. it seems that pri_pages_dirtied is always 0

src/childinfo.c

@@ -127,21 +127,9 @@ void receiveChildInfo(void) {
     int process_type;
     int on_exit;
     size_t cow_size;
-    if (readChildInfo(&process_type, &on_exit, &cow_size)) {
-        updateChildInfo(process_type, on_exit, cow_size);
-    }
-}
-
-/* Receive last COW data from child. */
-void receiveLastChildInfo(void) {
-    if (server.child_info_pipe[0] == -1) return;
-
-    /* Drain the pipe and update child info */
-    int process_type;
-    int on_exit;
-    size_t cow_size;
-
-    while (readChildInfo(&process_type, &on_exit, &cow_size) > 0) {
+
+    /* Drain the pipe and update child info so that we get the final message. */
+    while (readChildInfo(&process_type, &on_exit, &cow_size)) {
         updateChildInfo(process_type, on_exit, cow_size);
     }
 }

src/server.h

@@ -2013,7 +2013,6 @@ void openChildInfoPipe(void);
 void closeChildInfoPipe(void);
 void sendChildInfo(int process_type, int on_exit, size_t cow_size);
 void receiveChildInfo(void);
-void receiveLastChildInfo(void);
 
 /* Fork helpers */
 int redisFork(int type);

src/zmalloc.c

@@ -580,15 +580,18 @@ size_t zmalloc_get_smap_bytes_by_field(char *field, long pid) {
 size_t zmalloc_get_smap_bytes_by_field(char *field, long pid) {
 #if defined(__APPLE__)
     struct proc_regioninfo pri;
-    if (proc_pidinfo(pid, PROC_PIDREGIONINFO, 0, &pri, PROC_PIDREGIONINFO_SIZE) ==
-	PROC_PIDREGIONINFO_SIZE) {
-	if (!strcmp(field, "Private_Dirty:")) {
-            return (size_t)pri.pri_pages_dirtied * 4096;
-	} else if (!strcmp(field, "Rss:")) {
-            return (size_t)pri.pri_pages_resident * 4096;
-	} else if (!strcmp(field, "AnonHugePages:")) {
+    if (pid == -1) pid = getpid();
+    if (proc_pidinfo(pid, PROC_PIDREGIONINFO, 0, &pri,
+                     PROC_PIDREGIONINFO_SIZE) == PROC_PIDREGIONINFO_SIZE)
+    {
+        int pagesize = getpagesize();
+        if (!strcmp(field, "Private_Dirty:")) {
+            return (size_t)pri.pri_pages_dirtied * pagesize;
+        } else if (!strcmp(field, "Rss:")) {
+            return (size_t)pri.pri_pages_resident * pagesize;
+        } else if (!strcmp(field, "AnonHugePages:")) {
             return 0;
-	}
+        }
     }
     return 0;
 #endif

tests/integration/rdb.tcl

@@ -199,6 +199,10 @@ test {client freed during loading} {
     }
 }
 
+# Our COW metrics (Private_Dirty) work only on Linux
+set system_name [string tolower [exec uname -s]]
+if {$system_name eq {linux}} {
+
 start_server {overrides {save ""}} {
     test {Test child sending COW info} {
         # make sure that rdb_last_cow_size and current_cow_size are zero (the test using new server),
@@ -209,6 +213,7 @@ start_server {overrides {save ""}} {
         # using a 200us delay, the bgsave is empirically taking about 10 seconds.
         # we need it to take more than some 5 seconds, since redis only report COW once a second.
         r config set rdb-key-save-delay 200
+        r config set loglevel debug
 
         # populate the db with 10k keys of 4k each
         set rd [redis_deferring_client 0]
@@ -247,8 +252,9 @@ start_server {overrides {save ""}} {
             } else {
                 if {$::verbose} {
                     puts "COW info on fail: [s current_cow_size]"
+                    puts [exec tail -n 100 < [srv 0 stdout]]
                 }
-                fail "COW info didn't report"
+                fail "COW info wasn't reported"
             }
 
             # for no accurate, stop after 2 iterations
@@ -265,11 +271,21 @@ start_server {overrides {save ""}} {
         }
 
         # make sure we saw report of current_cow_size
+        if {$iteration < 2 && $::verbose} {
+            puts [exec tail -n 100 < [srv 0 stdout]]
+        }
         assert_morethan_equal $iteration 2
 
-        # if bgsave completed, check that rdb_last_cow_size value is at least as last rdb_active_cow_size.
+        # if bgsave completed, check that rdb_last_cow_size (fork exit report)
+        # is at least 90% of last rdb_active_cow_size.
         if { [s rdb_bgsave_in_progress] == 0 } {
-            assert_morethan_equal [s rdb_last_cow_size] $cow_size
+            set final_cow [s rdb_last_cow_size]
+            set cow_size [expr $cow_size * 0.9]
+            if {$final_cow < $cow_size && $::verbose} {
+                puts [exec tail -n 100 < [srv 0 stdout]]
+            }
+            assert_morethan_equal $final_cow $cow_size
         }
     }
-}
+}
+} ;# system_name