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Type: Bug
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Resolution: Incomplete
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Priority: Major - P3
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None
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Affects Version/s: None
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Component/s: WiredTiger
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None
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ALL
I have a 32 GB WT server running 3.0.8
The "bytes in cache" always seem to hover around ~1GB even though I have configured the cache size to be around ~26GB.
The total data size is around 40GB. Why is the rest of the cache not being used?
> db.serverStatus().wiredTiger.cache { "tracked dirty bytes in the cache" : 0, "tracked bytes belonging to internal pages in the cache" : 27634342, "bytes currently in the cache" : 950556531, "tracked bytes belonging to leaf pages in the cache" : 27889653082, "maximum bytes configured" : 27917287424, "tracked bytes belonging to overflow pages in the cache" : 0, "bytes read into cache" : 17875008775, "bytes written from cache" : 120063944822, "pages evicted by application threads" : 0, "checkpoint blocked page eviction" : 4, "unmodified pages evicted" : 0, "page split during eviction deepened the tree" : 1, "modified pages evicted" : 90924, "pages selected for eviction unable to be evicted" : 20, "pages evicted because they exceeded the in-memory maximum" : 1289, "pages evicted because they had chains of deleted items" : 14418, "failed eviction of pages that exceeded the in-memory maximum" : 15, "hazard pointer blocked page eviction" : 6, "internal pages evicted" : 0, "maximum page size at eviction" : 10499573, "eviction server candidate queue empty when topping up" : 1241, "eviction server candidate queue not empty when topping up" : 3, "eviction server evicting pages" : 0, "eviction server populating queue, but not evicting pages" : 1243, "eviction server unable to reach eviction goal" : 0, "pages split during eviction" : 1374, "pages walked for eviction" : 55451388, "eviction worker thread evicting pages" : 2086, "in-memory page splits" : 1238, "percentage overhead" : 8, "tracked dirty pages in the cache" : 0, "pages currently held in the cache" : 16807, "pages read into cache" : 2583552, "pages written from cache" : 7389684 }
The only thing special about this server is that it has a large number of dbs, around 4k. Each db has around 3 collections.