This morning we've been swamped by the following error messages:

Tue Jul 26 11:28:22 [conn1899] insert pankia_production.articles exception 13636 createPrivateMap failed (look in log for error) 6ms
Tue Jul 26 11:28:22 [conn1892] ERROR: mmap private failed with out of memory. (64 bit build)
Tue Jul 26 11:28:22 [conn1892] Assertion: 13636:createPrivateMap failed (look in log for error)
0x55f5aa 0x629030 0x62999c 0x7826aa 0x769d0b 0x76a0aa 0x76a2a0 0x779aee 0x77b4cf 0x7595bd 0x75b23f 0x8a8fce 0x8bb630 0x7fab0e45e8ba 0x7fab0da1a02d
/usr/bin/mongod(_ZN5mongo11msgassertedEiPKc+0x12a) [0x55f5aa]
/usr/bin/mongod(_ZN5mongo8MongoMMF13finishOpeningEv+0x60) [0x629030]
/usr/bin/mongod(_ZN5mongo8MongoMMF6createESsRyb+0x6c) [0x62999c]
/usr/bin/mongod(_ZN5mongo13MongoDataFile4openEPKcib+0x13a) [0x7826aa]
/usr/bin/mongod(_ZN5mongo8Database7getFileEiib+0x17b) [0x769d0b]
/usr/bin/mongod(_ZN5mongo8Database12suitableFileEib+0x3a) [0x76a0aa]
/usr/bin/mongod(_ZN5mongo8Database11allocExtentEPKcib+0x70) [0x76a2a0]
/usr/bin/mongod(_ZN5mongo11DataFileMgr6insertEPKcPKvibRKNS_11BSONElementEb+0x98e) [0x779aee]
/usr/bin/mongod(_ZN5mongo11DataFileMgr16insertWithObjModEPKcRNS_7BSONObjEb+0x5f) [0x77b4cf]
/usr/bin/mongod(_ZN5mongo14receivedInsertERNS_7MessageERNS_5CurOpE+0x37d) [0x7595bd]
/usr/bin/mongod(_ZN5mongo16assembleResponseERNS_7MessageERNS_10DbResponseERKNS_8SockAddrE+0x192f) [0x75b23f]
/usr/bin/mongod(_ZN5mongo10connThreadEPNS_13MessagingPortE+0x21e) [0x8a8fce]
/usr/bin/mongod(thread_proxy+0x80) [0x8bb630]
/lib/libpthread.so.0(+0x68ba) [0x7fab0e45e8ba]
/lib/libc.so.6(clone+0x6d) [0x7fab0da1a02d]

It didn't crash, but some write operation failed consistently.

Now we commented out "journal = true" line from /etc/mongodb.conf, and everything went back to normal, it seems. We've confirmed that if we set "journal = true" again, the above log start to appear again, so it's reproducible here.

The server has 4GB RAM on 64bit Linux, and there are 6.4GB of files under /var/lib/mongodb/.

If you need more info, let me know.