[SERVER-17035] fix text for "pages evicted by application threads" in WiredTiger Created: 24/Jan/15  Updated: 26/Jan/15  Resolved: 25/Jan/15

Status: Closed
Project: Core Server
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Task Priority: Minor - P4
Reporter: Mark Callaghan Assignee: Keith Bostic (Inactive)
Resolution: Duplicate Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Duplicate
duplicates SERVER-17020 Evictions by eviction server threads ... Closed
Backwards Compatibility: Fully Compatible
Participants:

 Description   

This is the cache section from db.serverStatus() after running a busy workload for about a few minutes. Note that mongod was started immediately prior to the test.

How can this possibly be true after a few minutes?
"pages evicted by application threads" : 3938125731,

I thought that maybe it counted bytes, which is possible given:
"bytes written from cache" : 4421343996,

But from looking at the code it just counts the number of calls to __wt_evict_lru_page

/*
 * __wt_evict_lru_page --
 *      Called by both eviction and application threads to evict a page.
 */
int
__wt_evict_lru_page(WT_SESSION_IMPL *session, int is_app)
{
        WT_BTREE *btree;
        WT_CACHE *cache;
        WT_DECL_RET;
        WT_PAGE *page;
        WT_REF *ref;
 
        if (is_app)
                WT_STAT_FAST_CONN_INCR(session, cache_eviction_app);

                "cache" : {
                        "tracked dirty bytes in the cache" : 488305732,
                        "bytes currently in the cache" : 857590757,
                        "maximum bytes configured" : 1073741824,
                        "bytes read into cache" : 6992771243,
                        "bytes written from cache" : 4421343996,
                        "pages evicted by application threads" : 3938125731,
                        "checkpoint blocked page eviction" : 3,
                        "unmodified pages evicted" : 199580,
                        "page split during eviction deepened the tree" : 1,
                        "modified pages evicted" : 65810,
                        "pages selected for eviction unable to be evicted" : 941,
                        "pages evicted because they exceeded the in-memory maximum" : 400,
                        "pages evicted because they had chains of deleted items" : 2,
                        "failed eviction of pages that exceeded the in-memory maximum" : 0,
                        "hazard pointer blocked page eviction" : 20,
                        "internal pages evicted" : 0,
                        "maximum page size at eviction" : 42848801,
                        "eviction server candidate queue empty when topping up" : 1092,
                        "eviction server candidate queue not empty when topping up" : 11153,
                        "eviction server evicting pages" : 59,
                        "eviction server populating queue, but not evicting pages" : 12186,
                        "eviction server unable to reach eviction goal" : 0,
                        "pages split during eviction" : 3919,
                        "pages walked for eviction" : 9457046,
                        "in-memory page splits" : 133,
                        "tracked dirty pages in the cache" : 7550,
                        "pages currently held in the cache" : 14340,
                        "pages read into cache" : 279087,
                        "pages written from cache" : 221121
                },



 Comments   
Comment by Daniel Pasette (Inactive) [ 25/Jan/15 ]

This was just noticed on Friday by us as well.
See: SERVER-17020. keith.bostic has a patch ready for it: https://github.com/wiredtiger/wiredtiger/pull/1596

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