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  1. Core Server
  2. SERVER-14544

can't apply newCollectionsUsePowerOf2Sizes=false, neither config entry nor mongo shell command nor mongod command seems to work

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Works as Designed
    • Affects Version/s: 2.6.1
    • Fix Version/s: None
    • Component/s: Storage
    • Labels:
      None
    • Operating System:
      ALL

      Description

      We are using v2.6.1 and learned that powerOf2Sizes is now the default memory allocation strategy (see also https://jira.mongodb.org/browse/CS-13109 ). However, we prefer not to use it because it consumes always 20% more RAM than the conventional mem alloc strategy.
      So, we added the folling line to our mongod.config, which is btw. badly documented, so perhaps we used the wrong syntax?

      setParameter=newCollectionsUsePowerOf2Sizes=false

      However I assume that's the right syntax since the mongod logs showed that the parameter was picked up successfully:

      2014-07-11T17:48:22.712+0200 ***** SERVER RESTARTED *****
      2014-07-11T17:48:22.727+0200 [initandlisten] MongoDB starting : pid=12808 port=27017 dbpath=/data/mongod/db 64-bit host=s488
      2014-07-11T17:48:22.736+0200 [initandlisten] db version v2.6.1
      2014-07-11T17:48:22.736+0200 [initandlisten] git version: 4b95b086d2374bdcfcdf2249272fb552c9c726e8
      2014-07-11T17:48:22.736+0200 [initandlisten] build info: Linux build14.nj1.10gen.cc 2.6.32-431.3.1.el6.x86_64 #1 SMP Fri Jan 3 21:39:27 UTC 2014 x86_64 BOOST_LIB_VERSION=1_49
      2014-07-11T17:48:22.736+0200 [initandlisten] allocator: tcmalloc
      2014-07-11T17:48:22.736+0200 [initandlisten] options: { config: "/etc/mongod_mongod.conf", net: { http: { RESTInterfaceEnabled: true, enabled: true }, port: 27017 }, processManagement: { pidFilePath: "/data/mongod/mongod.pid" }, replication: { replSet: "offerStoreDE5" }, security: { keyFile: "/data/keyfile.txt" }, setParameter: { newCollectionsUsePowerOf2Sizes: "false" }, storage: { dbPath: "/data/mongod/db", directoryPerDB: true, journal: { enabled: false } }, systemLog: { destination: "file", logAppend: true, path: "/data/mongod/log/mongod.log" } }
      2014-07-11T17:48:22.763+0200 [FileAllocator] allocating new datafile /data/mongod/db/local/local.ns, filling with zeroes...
      2014-07-11T17:48:22.763+0200 [FileAllocator] creating directory /data/mongod/db/local/_tmp
      2014-07-11T17:48:22.766+0200 [FileAllocator] done allocating datafile /data/mongod/db/local/local.ns, size: 16MB,  took 0 secs
      2014-07-11T17:48:22.768+0200 [FileAllocator] allocating new datafile /data/mongod/db/local/local.0, filling with zeroes...
      2014-07-11T17:48:22.768+0200 [FileAllocator] done allocating datafile /data/mongod/db/local/local.0, size: 64MB,  took 0 secs
      2014-07-11T17:48:22.770+0200 [initandlisten] build index on: local.startup_log properties: { v: 1, key: { _id: 1 }, name: "_id_", ns: "local.startup_log" }
      2014-07-11T17:48:22.770+0200 [initandlisten]     added index to empty collection
      2014-07-11T17:48:22.772+0200 [initandlisten] waiting for connections on port 27017
      2014-07-11T17:48:22.772+0200 [websvr] admin web console waiting for connections on port 28017
      2014-07-11T17:48:22.773+0200 [rsStart] replSet can't get local.system.replset config from self or any seed (EMPTYCONFIG)

      Before restarting mongod, we completely emptied the db directory, to be sure that all data will be allocated using the old memory allocation strategy.

      Two days later I wondered why RAM consumption was still very high and I discovered, that db.offer.stats().userFlags:1, which means that powerOf2Sizes is still used.
      So I executed the following command which I found in the doc to switch back to the old memory allocation strategy:

      offerStoreDE5:SECONDARY> db.getSiblingDB('admin').runCommand( { setParameter: 1, newCollectionsUsePowerOf2Sizes: false } )
      { "was" : false, "ok" : 1 }
      offerStoreDE5:SECONDARY>
      offerStoreDE5:SECONDARY> use offerStore
      switched to db offerStore
      offerStoreDE5:SECONDARY> db.offer.stats()
      {
              "ns" : "offerStore.offer",
              "count" : 55905283,
              "size" : 146846463152,
              "avgObjSize" : 2626,
              "storageSize" : 150970108880,
              "numExtents" : 91,
              "nindexes" : 10,
              "lastExtentSize" : 2146426864,
              "paddingFactor" : 1.0090000000000001,
              "systemFlags" : 1,
              "userFlags" : 1,
              "totalIndexSize" : 17563699552,
              "indexSizes" : {
                      "_id_" : 1449596624,
                      "bokey_1" : 3597717984,
                      "categoryBokey_1" : 2737545552,
                      "mappedCatalogCategory_1" : 1780765504,
                      "clickCount_1" : 1037501696,
                      "missingSince_1" : 1339891056,
                      "shopId_1_merchantId_1" : 2271668896,
                      "asin_1" : 533647520,
                      "importGroup_1_importId_1_missingSince_1" : 834442560,
                      "shopId_1__id_1" : 1980922160
              },
              "ok" : 1
      }

      However, db.offer.stats().userFlags is still 1, meaning that powerOf2Sizes is still used:

      offerStoreDE5:SECONDARY> db.offer.stats()
      {
              "ns" : "offerStore.offer",
              "count" : 55902199,
              "size" : 146841155952,
              "avgObjSize" : 2626,
              "storageSize" : 150970108880,
              "numExtents" : 91,
              "nindexes" : 10,
              "lastExtentSize" : 2146426864,
              "paddingFactor" : 1,
              "systemFlags" : 1,
              "userFlags" : 1,
              "totalIndexSize" : 17563740432,
              "indexSizes" : {
                      "_id_" : 1449596624,
                      "bokey_1" : 3597742512,
                      "categoryBokey_1" : 2737578256,
                      "mappedCatalogCategory_1" : 1780806384,
                      "clickCount_1" : 1037518048,
                      "missingSince_1" : 1339882880,
                      "shopId_1_merchantId_1" : 2271652544,
                      "asin_1" : 533663872,
                      "importGroup_1_importId_1_missingSince_1" : 834377152,
                      "shopId_1__id_1" : 1980922160
              },
              "ok" : 1
      }

      So I executed the other command I've found in the doc to switch back to the old memory allocation strategy:

      root@s488:/home/admin# mongod --setParameter newCollectionsUsePowerOf2Sizes=false
      2014-07-13T19:05:17.500+0200 [initandlisten] MongoDB starting : pid=58356 port=27017 dbpath=/data/db 64-bit host=s488
      2014-07-13T19:05:17.501+0200 [initandlisten]
      2014-07-13T19:05:17.501+0200 [initandlisten] ** WARNING: You are running on a NUMA machine.
      2014-07-13T19:05:17.501+0200 [initandlisten] **          We suggest launching mongod like this to avoid performance problems:
      2014-07-13T19:05:17.501+0200 [initandlisten] **              numactl --interleave=all mongod [other options]
      2014-07-13T19:05:17.517+0200 [initandlisten]
      2014-07-13T19:05:17.517+0200 [initandlisten] db version v2.6.1
      2014-07-13T19:05:17.517+0200 [initandlisten] git version: 4b95b086d2374bdcfcdf2249272fb552c9c726e8
      2014-07-13T19:05:17.517+0200 [initandlisten] build info: Linux build14.nj1.10gen.cc 2.6.32-431.3.1.el6.x86_64 #1 SMP Fri Jan 3 21:39:27 UTC 2014 x86_64 BOOST_LIB_VERSION=1_49
      2014-07-13T19:05:17.517+0200 [initandlisten] allocator: tcmalloc
      2014-07-13T19:05:17.517+0200 [initandlisten] options: { setParameter: { newCollectionsUsePowerOf2Sizes: "false" } }
      2014-07-13T19:05:17.529+0200 [initandlisten] exception in initAndListen: 10296
      *********************************************************************
       ERROR: dbpath (/data/db) does not exist.
       Create this directory or give existing directory in --dbpath.
       See http://dochub.mongodb.org/core/startingandstoppingmongo
      *********************************************************************
      , terminating
      2014-07-13T19:05:17.529+0200 [initandlisten] dbexit:
      2014-07-13T19:05:17.529+0200 [initandlisten] shutdown: going to close listening sockets...
      2014-07-13T19:05:17.529+0200 [initandlisten] shutdown: going to flush diaglog...
      2014-07-13T19:05:17.529+0200 [initandlisten] shutdown: going to close sockets...
      2014-07-13T19:05:17.529+0200 [initandlisten] shutdown: waiting for fs preallocator...
      2014-07-13T19:05:17.529+0200 [initandlisten] shutdown: lock for final commit...
      2014-07-13T19:05:17.529+0200 [initandlisten] shutdown: final commit...
      2014-07-13T19:05:17.529+0200 [initandlisten] shutdown: closing all files...
      2014-07-13T19:05:17.529+0200 [initandlisten] closeAllFiles() finished
      2014-07-13T19:05:17.529+0200 [initandlisten] dbexit: really exiting now
      root@s488:/home/admin# ps aux|grep mongo
      mongodb   12808 17.5 79.0 205348560 104490476 ? Sl   Jul11 518:38 /usr/bin/mongod --config /etc/mongod_mongod.conf
      root      58384  0.0  0.0  14760   920 pts/0    S+   19:05   0:00 grep mongo
      root@s488:/home/admin# 

      I'm also wondering why mongo is looking for /data/db because our dbPath is configured /data/mongod/db (see above the log when the server restarted).
      Furthermore, the mongod process was and is still running even though mongod pretended "dbexit: really exiting now".

      My main question is, how can I revert to the old memory allocation strategy? Neither config entry nor mongo shell command nor mongod command seems to work.

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