We have a MongoDb instance which contains two main db use about 30G of disk.
>show dbs;
admin (empty)
l_comment 17.945GB
l_recommend 15.946GB
lifeix_relation 1.953GB
local 2.077GB
test (empty)
Some time the mongostat command showed that the mongo use very much memory up to 61G in about 1 or 2 minutes (memory of the machine is 64G).
Below is some output of mongostat, it shows that there is no index miss during the time, but the date of column 'res' is growing fast, and res size is much bigger than db size showed use show dbs .
So what can cause this?
Thanks for any tips and help.
*0 29 1 *0 0 7|0 0 35.9g 72.3g 1.67g 0 l_comment:0.0% 0 0|0 0|0 4k 36k 121 PRI 12:24:58
*0 23 *0 *0 0 8|0 0 35.9g 72.3g 1.68g 0 l_comment:0.0% 0 0|0 0|0 4k 39k 121 PRI 12:24:59
*0 18 *0 *0 0 8|0 0 35.9g 72.3g 1.68g 0 l_comment:0.0% 0 0|0 0|0 3k 41k 121 PRI 12:25:00
*0 22 *0 *0 0 5|0 0 35.9g 72.3g 1.68g 1 l_comment:0.0% 0 0|0 0|0 3k 22k 121 PRI 12:25:01
1 21 4 *0 4 12|0 0 35.9g 72.3g 1.68g 0 l_comment:0.2% 0 0|0 0|0 4k 44k 121 PRI 12:25:02
1 15 4 *0 3 9|0 0 35.9g 72.3g 1.67g 0 l_comment:0.3% 0 0|0 0|0 3k 6k 121 PRI 12:25:03
*0 11 *0 *0 0 3|0 0 35.9g 72.3g 1.68g 0 l_comment:0.0% 0 0|0 0|0 1k 19k 121 PRI 12:25:04
insert query update delete getmore command flushes mapped vsize res faults locked db idx miss % qr|qw ar|aw netIn netOut conn repl time
1 30 5 *0 3 15|0 0 35.9g 72.5g 1.8g 0 l_comment:0.1% 0 0|0 1|0 5k 24k 121 PRI 12:25:05
*0 16 1 *0 1 6|0 0 35.9g 73.1g 2.45g 0 l_comment:0.0% 0 0|0 3|0 2k 15k 121 PRI 12:25:06
2 29 7 *0 6 17|0 0 35.9g 74.2g 3.56g 0 l_comment:0.5% 0 0|0 3|0 6k 38k 121 PRI 12:25:07
*0 13 1 *0 0 6|0 0 35.9g 74.9g 4.53g 0 l_comment:0.0% 0 0|0 6|0 1k 48k 121 PRI 12:25:08
2 27 6 *0 5 17|0 0 35.9g 75.5g 5.47g 0 l_comment:2.2% 0 0|0 9|0 5k 21k 121 PRI 12:25:09
1 25 6 *0 5 16|0 0 35.9g 75.7g 5.88g 1 l_comment:2.5% 0 0|0 13|0 5k 15k 121 PRI 12:25:10
2 39 7 *0 8 20|0 0 35.9g 77.4g 7.94g 0 l_comment:1.5% 0 0|0 14|0 7k 54k 121 PRI 12:25:11
*0 14 1 *0 0 6|0 0 35.9g 78.3g 7.86g 0 l_comment:4.8% 0 0|0 17|0 2k 37k 121 PRI 12:25:12
*0 15 *0 *0 0 8|0 0 35.9g 78.9g 9.51g 0 l_comment:0.0% 0 19|1 21|0 2k 29k 121 PRI 12:25:13
2 49 7 *0 8 23|0 0 35.9g 79.4g 10.7g 4 l_comment:0.2% 0 0|0 22|0 9k 46k 121 PRI 12:25:14
insert query update delete getmore command flushes mapped vsize res faults locked db idx miss % qr|qw ar|aw netIn netOut conn repl time
*0 21 *0 *0 0 10|0 0 35.9g 80.7g 11.2g 0 l_comment:5.8% 0 0|0 25|0 3k 36k 121 PRI 12:25:15
1 28 3 *0 4 13|0 0 35.9g 80.9g 11.7g 0 l_comment:0.2% 0 0|0 27|0 5k 44k 121 PRI 12:25:16
1 23 4 *0 4 16|0 0 35.9g 81g 11.9g 1 l_comment:0.5% 0 0|0 31|0 4k 30k 121 PRI 12:25:17
*0 19 1 *0 0 6|0 0 35.9g 81.5g 12.3g 8 l_comment:0.0% 0 37|1 38|0 2k 31k 121 PRI 12:25:18
*0 34 *0 *0 0 13|0 0 35.9g 82g 13.5g 2 l_comment:2.2% 0 31|0 35|0 6k 54k 121 PRI 12:25:19
*0 13 *0 *0 0 7|0 1 35.9g 82.9g 14.9g 0 l_comment:0.0% 0 36|0 38|0 2k 17k 121 PRI 12:25:20
*0 20 *0 *0 0 10|0 0 35.9g 84.5g 16.7g 0 l_comment:0.0% 0 33|0 39|0 3k 29k 121 PRI 12:25:21
*0 20 *0 *0 1 6|0 0 35.9g 85.6g 17.8g 1 l_comment:0.0% 0 31|0 40|0 3k 20k 121 PRI 12:25:22
*0 19 1 *0 1 5|0 0 35.9g 86.9g 19.4g 1 l_comment:0.0% 0 0|0 43|0 2k 16k 121 PRI 12:25:23
1 25 4 *0 5 14|0 0 35.9g 87.3g 19.9g 0 l_comment:0.2% 0 0|0 43|0 5k 23k 121 PRI 12:25:24
insert query update delete getmore command flushes mapped vsize res faults locked db idx miss % qr|qw ar|aw netIn netOut conn repl time
*0 28 3 *0 1 12|0 0 35.9g 88.1g 20.9g 1 l_comment:0.0% 0 43|1 44|0 5k 25k 121 PRI 12:25:25
*0 26 *0 *0 0 9|0 0 35.9g 89.1g 22g 0 l_comment:0.0% 0 0|0 46|0 4k 22k 121 PRI 12:25:26
*0 14 *0 *0 0 6|0 0 35.9g 89.1g 20.6g 1 l_comment:5.8% 0 0|0 48|0 2k 27k 121 PRI 12:25:27
*0 32 *0 *0 0 15|0 0 35.9g 89.1g 21g 3 l_comment:0.0% 0 68|1 6|0 3k 20k 121 PRI 12:25:28
1 35 4 *0 3 17|0 0 35.9g 89.8g 22.2g 2 l_comment:0.2% 0 0|0 58|0 8k 71k 121 PRI 12:25:29
*0 24 *0 *0 0 12|0 0 35.9g 89.8g 21.6g 0 l_comment:4.0% 0 0|0 64|0 4k 22k 121 PRI 12:25:30
*0 29 *0 *0 0 11|0 0 35.9g 89.9g 22.1g 0 l_comment:0.0% 0 74|1 75|0 4k 37k 121 PRI 12:25:32
1 40 4 *0 4 17|0 0 35.9g 90.7g 23.2g 14 l_comment:0.2% 0 25|0 48|0 8k 56k 121 PRI 12:25:33
*0 24 *0 *0 0 12|0 0 35.9g 91.8g 24.3g 20 l_comment:1.4% 0 41|0 73|0 3k 21k 121 PRI 12:25:34
1 23 4 *0 4 11|0 0 35.9g 92g 23.9g 6 l_comment:3.5% 0 47|0 68|0 4k 20k 121 PRI 12:25:35
insert query update delete getmore command flushes mapped vsize res faults locked db idx miss % qr|qw ar|aw netIn netOut conn repl time
*0 19 *0 *0 0 10|0 0 35.9g 93.2g 25.5g 0 l_comment:0.0% 0 54|0 80|0 3k 24k 121 PRI 12:25:36
*0 17 *0 *0 0 5|0 0 35.9g 94.6g 26.1g 0 l_comment:3.7% 0 88|0 88|0 1k 9k 121 PRI 12:25:37
*0 31 *0 *0 0 9|0 0 35.9g 95.4g 27.4g 3 l_comment:0.0% 0 32|0 83|0 5k 52k 121 PRI 12:25:38
*0 35 3 *0 1 12|0 0 35.9g 96.4g 29g 1 l_comment:0.0% 0 29|0 85|0 6k 56k 121 PRI 12:25:39
*0 15 *0 *0 0 9|0 0 35.9g 97.6g 30.6g 0 l_comment:0.2% 0 53|0 87|0 2k 12k 121 PRI 12:25:40
*0 32 *0 *0 0 11|0 0 35.9g 98.7g 32.1g 8 l_comment:0.0% 0 61|0 93|0 5k 56k 121 PRI 12:25:41
1 33 4 *0 4 9|0 0 35.9g 99.9g 33.3g 19 l_comment:0.1% 0 55|0 90|0 6k 26k 121 PRI 12:25:42
*0 12 *0 *0 0 4|0 0 35.9g 100g 31.9g 1 l_comment:0.0% 0 104|0 104|0 841b 12k 121 PRI 12:25:43
*0 20 5 *0 2 12|0 0 35.9g 101g 32.8g 0 l_comment:6.9% 0 98|1 100|0 5k 23k 121 PRI 12:25:44
*0 18 *0 *0 0 4|0 0 35.9g 101g 33.2g 1 l_comment:0.1% 0 93|1 99|0 3k 39k 121 PRI 12:25:46
insert query update delete getmore command flushes mapped vsize res faults locked db idx miss % qr|qw ar|aw netIn netOut conn repl time
*0 2 *0 *0 0 2|0 0 35.9g 101g 33.6g 0 l_comment:0.0% 0 69|0 93|0 490b 13k 121 PRI 12:25:47
*0 9 *0 *0 0 1|0 0 35.9g 101g 34.3g 0 l_comment:0.1% 0 66|0 95|0 966b 4k 121 PRI 12:25:48
*0 8 *0 *0 1 1|0 0 35.9g 101g 34.7g 4 l_comment:0.0% 0 0|0 100|0 932b 6k 121 PRI 12:25:49
*0 7 *0 *0 0 2|0 0 35.9g 102g 36g 0 l_comment:0.0% 0 0|0 100|0 724b 3k 121 PRI 12:25:50
*0 5 *0 *0 0 1|0 0 35.9g 104g 37.2g 1 l_comment:0.0% 0 99|1 101|0 556b 4k 121 PRI 12:25:52
*0 10 *0 *0 0 1|0 0 35.9g 104g 37.5g 0 l_comment:0.1% 0 79|0 91|0 1k 4k 121 PRI 12:25:53
*0 2 *0 *0 0 1|0 0 35.9g 104g 37.6g 0 l_comment:0.0% 0 45|0 69|0 267b 4k 121 PRI 12:25:54
*0 5 *0 *0 1 1|0 0 35.9g 105g 39g 2 l_comment:0.0% 0 15|0 86|0 600b 5k 121 PRI 12:25:55
*0 3 1 *0 1 1|0 0 35.9g 107g 40.6g 0 l_comment:0.0% 0 0|0 100|1 395b 4k 121 PRI 12:25:56
*0 8 *0 *0 0 1|0 0 35.9g 108g 41.8g 3 l_comment:0.0% 0 100|1 101|0 845b 39k 121 PRI 12:25:57
insert query update delete getmore command flushes mapped vsize res faults locked db idx miss % qr|qw ar|aw netIn netOut conn repl time
*0 4 *0 *0 0 1|0 0 35.9g 108g 42.6g 0 l_comment:0.1% 0 0|0 100|0 472b 3k 121 PRI 12:25:58
*0 7 *0 *0 0 1|0 0 35.9g 108g 42.7g 2 l_comment:0.0% 0 0|0 100|0 821b 7k 121 PRI 12:25:59
*0 5 *0 *0 0 1|0 0 35.9g 109g 43.4g 0 l_comment:0.0% 0 101|1 104|0 304b 4k 121 PRI 12:26:01
*0 6 *0 *0 0 1|0 0 35.9g 109g 43.4g 1 l_comment:0.0% 0 97|1 100|0 966b 5k 121 PRI 12:26:02
*0 3 *0 *0 1 1|0 0 35.9g 110g 44.2g 1 l_comment:0.0% 0 97|1 100|0 438b 3k 121 PRI 12:26:03
*0 7 *0 *0 0 1|0 0 35.9g 110g 44.7g 2 l_comment:0.0% 0 0|0 100|0 724b 6k 121 PRI 12:26:04
*0 7 2 *0 1 4|0 0 35.9g 111g 44.8g 0 l_comment:0.0% 0 0|0 100|0 1k 4k 121 PRI 12:26:05
*0 5 1 *0 0 1|0 0 35.9g 111g 45.3g 2 l_comment:0.0% 0 103|1 104|0 304b 4k 121 PRI 12:26:06
*0 8 2 *0 1 3|0 0 35.9g 112g 46g 4 l_comment:0.1% 0 98|1 100|0 1k 80k 121 PRI 12:26:08
*0 5 1 *0 0 1|0 0 35.9g 112g 46.6g 0 l_comment:0.0% 0 66|0 88|0 593b 4k 121 PRI 12:26:09
insert query update delete getmore command flushes mapped vsize res faults locked db idx miss % qr|qw ar|aw netIn netOut conn repl time
*0 4 *0 *0 0 1|0 0 35.9g 112g 46.6g 0 l_comment:0.0% 0 0|0 100|0 472b 3k 121 PRI 12:26:10
*0 *0 *0 *0 0 1|0 0 35.9g 112g 46.7g 0 l_comment:0.0% 0 99|1 100|0 62b 3k 121 PRI 12:26:12
*0 9 3 *0 2 3|0 0 35.9g 112g 46.9g 1 l_comment:0.0% 0 52|0 68|0 1k 5k 121 PRI 12:26:13
*0 2 *0 *0 0 1|0 0 35.9g 112g 47g 0 l_comment:0.1% 0 71|0 88|0 267b 3k 121 PRI 12:26:14
*0 *0 *0 *0 0 1|0 0 35.9g 112g 47.1g 0 l_comment:0.0% 0 100|1 101|0 62b 3k 121 PRI 12:26:15
*0 4 *0 *0 0 1|0 0 35.9g 113g 47.3g 0 l_comment:0.0% 0 25|0 69|0 472b 3k 121 PRI 12:26:16
*0 5 *0 *0 0 1|0 0 35.9g 114g 48.3g 0 l_comment:0.0% 0 98|1 100|0 556b 3k 121 PRI 12:26:17
*0 4 *0 *0 0 1|0 0 35.9g 114g 49g 2 l_comment:0.0% 0 76|0 92|0 472b 8k 121 PRI 12:26:18
*0 3 *0 *0 1 1|0 0 35.9g 115g 49.9g 0 l_comment:0.0% 0 67|0 87|0 438b 3k 121 PRI 12:26:19
*0 3 *0 *0 0 2|0 1 35.9g 115g 49.9g 0 l_comment:0.1% 0 0|0 100|0 351b 3k 121 PRI 12:26:20
insert query update delete getmore command flushes mapped vsize res faults locked db idx miss % qr|qw ar|aw netIn netOut conn repl time
*0 *0 *0 *0 0 1|0 0 35.9g 115g 49.9g 0 l_comment:0.0% 0 95|1 100|0 62b 3k 121 PRI 12:26:22
*0 16 *0 *0 0 1|0 0 35.9g 115g 49.9g 0 l_comment:0.0% 0 101|1 102|0 966b 4k 121 PRI 12:26:23
*0 2 2 *0 1 2|0 0 35.9g 115g 50.1g 2 l_comment:0.0% 0 97|1 100|0 883b 5k 121 PRI 12:26:25
*0 3 *0 *0 0 1|0 0 35.9g 115g 50.1g 3 l_comment:0.1% 0 95|1 100|0 388b 4k 121 PRI 12:26:27
*0 8 *0 *0 0 1|0 0 35.9g 115g 50.2g 1 l_comment:0.0% 0 96|1 101|0 761b 4k 121 PRI 12:26:29
*0 3 *0 *0 0 1|0 0 35.9g 115g 50.2g 1 l_comment:0.0% 0 99|1 100|0 472b 18k 121 PRI 12:26:31
*0 5 *0 *0 1 1|0 0 35.9g 115g 50.3g 0 l_comment:0.0% 0 92|1 100|0 643b 4k 121 PRI 12:26:33
*0 9 *0 *0 0 1|0 0 35.9g 115g 50.3g 0 l_comment:0.0% 0 61|0 83|0 1k 5k 121 PRI 12:26:34
*0 5 2 *0 1 3|0 0 35.9g 115g 50.3g 0 l_comment:0.0% 0 0|0 100|0 1k 4k 121 PRI 12:26:35
*0 2 1 *0 0 2|0 0 35.9g 115g 50.3g 0 l_comment:0.0% 0 99|1 102|0 183b 3k 121 PRI 12:26:37
insert query update delete getmore command flushes mapped vsize res faults locked db idx miss % qr|qw ar|aw netIn netOut conn repl time
*0 3 1 *0 1 1|0 0 35.9g 115g 50.4g 1 l_comment:0.0% 0 96|1 100|0 559b 4k 121 PRI 12:26:39
*0 5 *0 *0 0 1|0 0 35.9g 115g 50.4g 3 l_comment:0.0% 0 98|1 100|0 550b 4k 121 PRI 12:26:41
*0 4 *0 *0 0 1|0 0 35.9g 115g 50.4g 0 l_comment:0.0% 0 98|1 100|0 472b 5k 121 PRI 12:26:42
*0 16 3 *0 2 3|0 0 35.9g 115g 50.4g 1 l_comment:0.0% 0 95|1 100|0 2k 5k 121 PRI 12:26:45
*0 8 *0 *0 0 1|0 0 35.9g 115g 50.5g 1 l_comment:0.0% 0 98|1 100|0 876b 11k 121 PRI 12:26:47
*0 3 *0 *0 0 1|0 0 35.9g 115g 50.5g 0 l_comment:0.0% 0 96|1 100|0 345b 5k 121 PRI 12:26:49
1 19 1 *0 4 10|0 0 35.9g 115g 50.5g 2 l_comment:0.0% 0 26|0 44|0 4k 23k 121 PRI 12:26:50
*0 *0 1 *0 0 2|0 0 35.9g 115g 50.5g 0 l_comment:0.0% 0 0|0 100|0 62b 3k 121 PRI 12:26:51
*0 *0 *0 *0 0 1|0 0 35.9g 115g 48g 0 l_comment:15.8% 0 0|0 100|0 62b 3k 121 PRI 12:26:52
*0 2 *0 *0 0 1|0 0 35.9g 115g 48.9g 1 l_comment:0.1% 0 0|0 100|0 267b 4k 121 PRI 12:26:53
insert query update delete getmore command flushes mapped vsize res faults locked db idx miss % qr|qw ar|aw netIn netOut conn repl time
*0 *0 *0 *0 0 1|0 0 35.9g 115g 49.3g 0 l_comment:0.0% 0 0|0 100|0 62b 3k 121 PRI 12:26:54
*0 *0 *0 *0 1 1|0 0 35.9g 115g 49.6g 0 l_comment:0.0% 0 0|0 100|0 112b 3k 121 PRI 12:26:55
*0 4 3 *0 1 3|0 0 35.9g 115g 49.9g 0 l_comment:0.1% 0 0|0 100|0 1k 4k 121 PRI 12:26:56
*0 2 *0 *0 0 1|0 0 35.9g 115g 50.1g 0 l_comment:0.0% 0 0|0 100|0 230b 3k 121 PRI 12:26:57
*0 7 *0 *0 0 1|0 0 35.9g 115g 50.2g 0 l_comment:0.0% 0 0|0 100|0 718b 3k 121 PRI 12:26:58
*0 4 *0 *0 0 1|0 0 35.9g 115g 50.4g 1 l_comment:0.0% 0 0|0 100|0 472b 3k 121 PRI 12:26:59
*0 2 *0 *0 0 1|0 0 35.9g 115g 50.4g 0 l_comment:0.0% 0 95|0 100|0 363b 3k 121 PRI 12:27:00
*0 7 *0 *0 1 3|0 0 35.9g 115g 50.4g 0 l_comment:0.0% 0 79|0 92|0 1k 4k 121 PRI 12:27:01
*0 4 *0 *0 0 1|0 0 35.9g 115g 50.4g 0 l_comment:0.0% 0 83|0 98|0 509b 4k 121 PRI 12:27:02
*0 1 *0 *0 0 1|0 0 35.9g 115g 50.4g 0 l_comment:0.0% 0 96|0 100|0 242b 3k 121 PRI 12:27:03
insert query update delete getmore command flushes mapped vsize res faults locked db idx miss % qr|qw ar|aw netIn netOut conn repl time
*0 4 *0 *0 0 1|0 0 35.9g 115g 50.4g 0 l_comment:0.1% 0 85|0 99|0 429b 4k 121 PRI 12:27:04
*0 1 1 *0 1 1|0 0 35.9g 115g 50.5g 0 l_comment:0.0% 0 0|0 100|0 233b 3k 121 PRI 12:27:05
*0 5 2 *0 1 3|0 0 35.9g 115g 50.5g 0 l_comment:0.0% 0 0|0 100|0 828b 4k 121 PRI 12:27:06
below is server status at time 12:25 and 12:26 , I can not find information useful about the problem.
limit to body length, I can only paste once of the output.
{ "host" : "mongodb-zhaowei-bj-201-56.chosk.net",
"version" : "2.6.4",
"process" : "mongod",
"pid" : { "$numberLong" : "26229" },
"uptime" : 13981,
"uptimeMillis" : { "$numberLong" : "13981035" },
"uptimeEstimate" : 13871,
"localTime" : { "$date" : "2014-10-16T12:25:01.407+0800" },
"asserts" : { "regular" : 0,
"warning" : 0,
"msg" : 0,
"user" : 14025,
"rollovers" : 0 },
"backgroundFlushing" : { "flushes" : 233,
"total_ms" : 381,
"average_ms" : 1.63519313304721,
"last_ms" : 2,
"last_finished" : { "$date" : "2014-10-16T12:25:00.431+0800" } },
"connections" : { "current" : 102,
"available" : 2298,
"totalCreated" : { "$numberLong" : "1037" } },
"cursors" : { "note" : "deprecated, use server status metrics",
"clientCursors_size" : 1,
"totalOpen" : 1,
"pinned" : 0,
"totalNoTimeout" : 0,
"timedOut" : 1 },
"dur" : { "commits" : 30,
"journaledMB" : 0.032768,
"writeToDataFilesMB" : 0.010758,
"compression" : 2.839268694220605,
"commitsInWriteLock" : 0,
"earlyCommits" : 0,
"timeMs" : { "dt" : 3069,
"prepLogBuffer" : 0,
"writeToJournal" : 1,
"writeToDataFiles" : 0,
"remapPrivateView" : 0 } },
"extra_info" : { "note" : "fields vary by platform",
"heap_usage_bytes" : 68060432,
"page_faults" : 89955 },
"globalLock" : { "totalTime" : { "$numberLong" : "13981043000" },
"lockTime" : { "$numberLong" : "3453729" },
"currentQueue" : { "total" : 0,
"readers" : 0,
"writers" : 0 },
"activeClients" : { "total" : 0,
"readers" : 0,
"writers" : 0 } },
"indexCounters" : { "accesses" : 772667,
"hits" : 772666,
"misses" : 0,
"resets" : 0,
"missRatio" : 0 },
"locks" : { "." : { "timeLockedMicros" : { "R" : { "$numberLong" : "488804" },
"W" : { "$numberLong" : "3453729" } },
"timeAcquiringMicros" : { "R" : { "$numberLong" : "691499" },
"W" : { "$numberLong" : "13208190" } } },
"admin" : { "timeLockedMicros" : { "r" : { "$numberLong" : "72766" },
"w" : { "$numberLong" : "0" } },
"timeAcquiringMicros" : { "r" : { "$numberLong" : "2268880" },
"w" : { "$numberLong" : "0" } } },
"local" : { "timeLockedMicros" : { "r" : { "$numberLong" : "714499" },
"w" : { "$numberLong" : "1422409" } },
"timeAcquiringMicros" : { "r" : { "$numberLong" : "21035232" },
"w" : { "$numberLong" : "1946197" } } },
"l_comment" : { "timeLockedMicros" : { "r" : { "$numberLong" : "259016933" },
"w" : { "$numberLong" : "8179608" } },
"timeAcquiringMicros" : { "r" : { "$numberLong" : "284944268" },
"w" : { "$numberLong" : "8533230" } } },
"l_recommend" : { "timeLockedMicros" : { "r" : { "$numberLong" : "202152" },
"w" : { "$numberLong" : "279" } },
"timeAcquiringMicros" : { "r" : { "$numberLong" : "29442" },
"w" : { "$numberLong" : "14" } } },
"lifeix_relation" : { "timeLockedMicros" : { "r" : { "$numberLong" : "81257" },
"w" : { "$numberLong" : "168" } },
"timeAcquiringMicros" : { "r" : { "$numberLong" : "30018" },
"w" : { "$numberLong" : "6" } } } },
"network" : { "bytesIn" : 64549227,
"bytesOut" : 525529045,
"numRequests" : 496002 },
"opcounters" : { "insert" : 4440,
"query" : 304833,
"update" : 18272,
"delete" : 8,
"getmore" : 16192,
"command" : 143477 },
"opcountersRepl" : { "insert" : 0,
"query" : 0,
"update" : 0,
"delete" : 0,
"getmore" : 0,
"command" : 0 },
"recordStats" : { "accessesNotInMemory" : 8390,
"pageFaultExceptionsThrown" : 1208,
"admin" : { "accessesNotInMemory" : 0,
"pageFaultExceptionsThrown" : 0 },
"l_comment" : { "accessesNotInMemory" : 8386,
"pageFaultExceptionsThrown" : 1208 },
"l_recommend" : { "accessesNotInMemory" : 3,
"pageFaultExceptionsThrown" : 0 },
"lifeix_relation" : { "accessesNotInMemory" : 0,
"pageFaultExceptionsThrown" : 0 },
"local" : { "accessesNotInMemory" : 1,
"pageFaultExceptionsThrown" : 0 } },
"repl" : { "ismaster" : true },
"writeBacksQueued" : false,
"mem" : { "bits" : 64,
"resident" : 619,
"virtual" : 74035,
"supported" : true,
"mapped" : 36785,
"mappedWithJournal" : 73570 },
"metrics" : { "cursor" : { "timedOut" : { "$numberLong" : "1" },
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Best Answer
MongoDB makes good use of your RAM. As long there is free RAM, it will take it. It will first try to get the indices into RAM. You can see their size with
from the mongo shell.
Next it will try to keep as much as possible of your working set in RAM (which is a bit simplified, but sufficient for this explanation).
MongoDB does all this to improve performance, which is a good thing. It does not make much sense to have free RAM I'd,Ingrid around because it might be possible that some other process might need it in the future. It is much better to utilize the RAM available and free it on demand. Which is a bit of the discussion between Windows and UNIX memory usage patterns. Judging from that, I'd assume you run MongoDB on a Windows machine ;).
The spikes you are experiencing usually happen under more or less high load. As long as there is no impact on other processes, there is nothing to worry about. If other processes are impacted, I'd strongly suggest migrating them or MongoDB to a dedicated machine/instance/VM. Please read the MongoDB Production Notes for details on how to set up optimal machines for MongoDB.