From 49b645235100fc214468b608c1ba6cdbc320fa88 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Mon, 19 Nov 2012 12:02:08 +0100
Subject: [PATCH] Children creating AOF or RDB files now report memory used by
 COW.

Finally Redis is able to report the amount of memory used by
copy-on-write while saving an RDB or writing an AOF file in background.

Note that this information is currently only logged (at NOTICE level)
and not shown in INFO because this is less trivial (but surely doable
with some minor form of interprocess communication).

The reason we can't capture this information on the parent before we
call wait3() is that the Linux kernel will release the child memory
ASAP, and only retain the minimal state for the process that is useful
to report the child termination to the parent.

The COW size is obtained by summing all the Private_Dirty fields found
in the "smap" file inside the proc filesystem for the process.

All this is Linux specific and is not available on other systems.
---
 src/aof.c | 7 +++++++
 src/rdb.c | 9 +++++++++
 2 files changed, 16 insertions(+)

diff --git a/src/aof.c b/src/aof.c
index bc92cdb9..6289e4dd 100644
--- a/src/aof.c
+++ b/src/aof.c
@@ -962,6 +962,13 @@ int rewriteAppendOnlyFileBackground(void) {
         if (server.sofd > 0) close(server.sofd);
         snprintf(tmpfile,256,"temp-rewriteaof-bg-%d.aof", (int) getpid());
         if (rewriteAppendOnlyFile(tmpfile) == REDIS_OK) {
+            size_t private_dirty = zmalloc_get_private_dirty();
+
+            if (private_dirty) {
+                redisLog(REDIS_NOTICE,
+                    "AOF rewrite: %lu MB of memory used by copy-on-write",
+                    private_dirty/(1024*1024));
+            }
             exitFromChild(0);
         } else {
             exitFromChild(1);
diff --git a/src/rdb.c b/src/rdb.c
index 193ff5b3..5a08b634 100644
--- a/src/rdb.c
+++ b/src/rdb.c
@@ -731,6 +731,15 @@ int rdbSaveBackground(char *filename) {
         if (server.ipfd > 0) close(server.ipfd);
         if (server.sofd > 0) close(server.sofd);
         retval = rdbSave(filename);
+        if (retval == REDIS_OK) {
+            size_t private_dirty = zmalloc_get_private_dirty();
+
+            if (private_dirty) {
+                redisLog(REDIS_NOTICE,
+                    "RDB: %lu MB of memory used by copy-on-write",
+                    private_dirty/(1024*1024));
+            }
+        }
         exitFromChild((retval == REDIS_OK) ? 0 : 1);
     } else {
         /* Parent */
-- 
2.47.2