verison：4.0.9
replicaset，3 node
primary node 's max memory:4GB
but info from mongostat output follows:
show dbs output:
PRIMARY> show dbs;
admin 0.000GB
config 0.000GB
xxx 0.013GB
local 0.342GB
why primary instance 's memory so high?
PRIMARY> db.serverStatus().tcmalloc
{
"generic" : {
"current_allocated_bytes" : NumberLong("36921151424"),
"heap_size" : NumberLong("40264519680")
},
"tcmalloc" : {
"pageheap_free_bytes" : NumberLong(1460367360),
"pageheap_unmapped_bytes" : NumberLong(1508446208),
"max_total_thread_cache_bytes" : NumberLong(1073741824),
"current_total_thread_cache_bytes" : 11085832,
"total_free_bytes" : 374554688,
"central_cache_free_bytes" : 358786648,
"transfer_cache_free_bytes" : 4682208,
"thread_cache_free_bytes" : 11085832,
"aggressive_memory_decommit" : 0,
"pageheap_committed_bytes" : NumberLong("38756073472"),
"pageheap_scavenge_count" : 1558237,
"pageheap_commit_count" : 4035069,
"pageheap_total_commit_bytes" : NumberLong("681721012224"),
"pageheap_decommit_count" : 1558514,
"pageheap_total_decommit_bytes" : NumberLong("642964938752"),
"pageheap_reserve_count" : 20923,
"pageheap_total_reserve_bytes" : NumberLong("40264519680"),
"spinlock_total_delay_ns" : NumberLong("10426415504"),
"formattedString" : "------------------------------------------------\nMALLOC: 36921152000 (35210.8 MiB) Bytes in use by application\nMALLOC: + 1460367360 ( 1392.7 MiB) Bytes in page heap freelist\nMALLOC: + 358786648 ( 342.2 MiB) Bytes in central cache freelist\nMALLOC: + 4682208 ( 4.5 MiB) Bytes in transfer cache freelist\nMALLOC: + 11085256 ( 10.6 MiB) Bytes in thread cache freelists\nMALLOC: + 336584960 ( 321.0 MiB) Bytes in malloc metadata\nMALLOC: ------------\nMALLOC: = 39092658432 (37281.7 MiB) Actual memory used (physical + swap)\nMALLOC: + 1508446208 ( 1438.6 MiB) Bytes released to OS (aka unmapped)\nMALLOC: ------------\nMALLOC: = 40601104640 (38720.2 MiB) Virtual address space used\nMALLOC:\nMALLOC: 5221570 Spans in use\nMALLOC: 82 Thread heaps in use\nMALLOC: 4096 Tcmalloc page size\n------------------------------------------------\nCall ReleaseFreeMemory() to release freelist memory to the OS (via madvise()).\nBytes released to the OS take up virtual address space but no physical memory.\n"
7fc4f4f24000-7fce68a61000 rw-p 00000000 00:00 0
Size: 39644404 kB
Rss: 37846436 kB
Pss: 37846436 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 37846436 kB
Referenced: 37278820 kB
Anonymous: 37846436 kB
AnonHugePages: 0 kB
Swap: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
{
"application threads page read from disk to cache count" : 146,
"application threads page read from disk to cache time (usecs)" : 6604,
"application threads page write from cache to disk count" : 17030483,
"application threads page write from cache to disk time (usecs)" : 698950227,
"bytes belonging to page images in the cache" : 3638217,
"bytes belonging to the cache overflow table in the cache" : 182,
"bytes currently in the cache" : 2252442633,
"bytes dirty in the cache cumulative" : NumberLong("18672485991968"),
"bytes not belonging to page images in the cache" : 2248804415,
"bytes read into cache" : 3367237,
"bytes written from cache" : 125547076860,
"cache overflow cursor application thread wait time (usecs)" : 0,
"cache overflow cursor internal thread wait time (usecs)" : 0,
"cache overflow score" : 57,
"cache overflow table entries" : 0,
"cache overflow table insert calls" : 0,
"cache overflow table remove calls" : 0,
"checkpoint blocked page eviction" : 717,
"eviction calls to get a page" : 7284869,
"eviction calls to get a page found queue empty" : 7284049,
"eviction calls to get a page found queue empty after locking" : 0,
"eviction currently operating in aggressive mode" : 0,
"eviction empty score" : 0,
"eviction passes of a file" : 0,
"eviction server candidate queue empty when topping up" : 0,
"eviction server candidate queue not empty when topping up" : 0,
"eviction server evicting pages" : 0,
"eviction server slept, because we did not make progress with eviction" : 28068,
"eviction server unable to reach eviction goal" : 0,
"eviction state" : 32,
"eviction walk target pages histogram - 0-9" : 0,
"eviction walk target pages histogram - 10-31" : 0,
"eviction walk target pages histogram - 128 and higher" : 0,
"eviction walk target pages histogram - 32-63" : 0,
"eviction walk target pages histogram - 64-128" : 0,
"eviction walks abandoned" : 0,
"eviction walks gave up because they restarted their walk twice" : 0,
"eviction walks gave up because they saw too many pages and found no candidates" : 0,
"eviction walks gave up because they saw too many pages and found too few candidates" : 0,
"eviction walks reached end of tree" : 0,
"eviction walks started from root of tree" : 0,
"eviction walks started from saved location in tree" : 0,
"eviction worker thread active" : 4,
"eviction worker thread created" : 0,
"eviction worker thread evicting pages" : 164,
"eviction worker thread removed" : 0,
"eviction worker thread stable number" : 0,
"failed eviction of pages that exceeded the in-memory maximum count" : 7,
"failed eviction of pages that exceeded the in-memory maximum time (usecs)" : 48,
"files with active eviction walks" : 0,
"files with new eviction walks started" : 0,
"force re-tuning of eviction workers once in a while" : 0,
"hazard pointer blocked page eviction" : 7,
"hazard pointer check calls" : 145606,
"hazard pointer check entries walked" : 484,
"hazard pointer maximum array length" : 1,
"in-memory page passed criteria to be split" : 591,
"in-memory page splits" : 282,
"internal pages evicted" : 0,
"internal pages split during eviction" : 0,
"leaf pages split during eviction" : 2,
"maximum bytes configured" : 4294967296,
"maximum page size at eviction" : 0,
"modified pages evicted" : 145331,
"modified pages evicted by application threads" : 0,
"operations timed out waiting for space in cache" : 0,
"overflow pages read into cache" : 0,
"page split during eviction deepened the tree" : 0,
"page written requiring cache overflow records" : 0,
"pages currently held in the cache" : 526,
"pages evicted because they exceeded the in-memory maximum count" : 145406,
"pages evicted because they exceeded the in-memory maximum time (usecs)" : 2618210631,
"pages evicted because they had chains of deleted items count" : 29,
"pages evicted because they had chains of deleted items time (usecs)" : 37391,
"pages evicted by application threads" : 0,
"pages queued for eviction" : 0,
"pages queued for urgent eviction" : 164,
"pages queued for urgent eviction during walk" : 0,
"pages read into cache" : 159,
"pages read into cache after truncate" : 122,
"pages read into cache after truncate in prepare state" : 0,
"pages read into cache requiring cache overflow entries" : 0,
"pages read into cache requiring cache overflow for checkpoint" : 0,
"pages read into cache skipping older cache overflow entries" : 0,
"pages read into cache with skipped cache overflow entries needed later" : 0,
"pages read into cache with skipped cache overflow entries needed later by checkpoint" : 0,
"pages requested from the cache" : 1275199575,
"pages seen by eviction walk" : 0,
"pages selected for eviction unable to be evicted" : 7,
"pages walked for eviction" : 0,
"pages written from cache" : 17030484,
"pages written requiring in-memory restoration" : 145166,
"percentage overhead" : 8,
"tracked bytes belonging to internal pages in the cache" : 63250,
"tracked bytes belonging to leaf pages in the cache" : 2252379383,
"tracked dirty bytes in the cache" : 2704172,
"tracked dirty pages in the cache" : 1,
"unmodified pages evicted" : 0
}
“bytes currently in the cache” : 2252442633,