Memcached What memcached cache by default installation?

by default Memcached doesn't cache anything, it's there for end users to use and configure themselves just like Nginx and PHP-FPM is there for end users to setup and tune for themselves

 

Yup that is correct PHP opcode caches cache automatically for PHP.

 

For me memcached used for Xenforo backend/sessions and ngx_pagespeed caching http://centminmod.com/nginx_ngx_pagespeed.html

i.e. memcached stats and ngx_pagespeed memcached stats

Code:

echo stats | nc 127.0.0.1 11211
STAT pid 24893
STAT uptime 1427018
STAT time 1403848397
STAT version 1.4.20
STAT libevent 2.0.21-stable
STAT pointer_size 64
STAT rusage_user 293.166637
STAT rusage_system 588.046607
STAT curr_connections 5
STAT total_connections 432303
STAT connection_structures 20
STAT reserved_fds 10
STAT cmd_get 10686238
STAT cmd_set 581530
STAT cmd_flush 43
STAT cmd_touch 0
STAT get_hits 10506060
STAT get_misses 180178
STAT delete_misses 0
STAT delete_hits 278
STAT incr_misses 0
STAT incr_hits 0
STAT decr_misses 0
STAT decr_hits 0
STAT cas_misses 0
STAT cas_hits 0
STAT cas_badval 0
STAT touch_hits 0
STAT touch_misses 0
STAT auth_cmds 0
STAT auth_errors 0
STAT bytes_read 4699609314
STAT bytes_written 57139407528
STAT limit_maxbytes 838860800
STAT accepting_conns 1
STAT listen_disabled_num 0
STAT threads 2
STAT conn_yields 0
STAT hash_power_level 16
STAT hash_bytes 524288
STAT hash_is_expanding 0
STAT slab_reassign_running 0
STAT slabs_moved 0
STAT malloc_fails 0
STAT bytes 177849734
STAT curr_items 34135
STAT total_items 581530
STAT expired_unfetched 46768
STAT evicted_unfetched 0
STAT evictions 0
STAT reclaimed 87641
STAT crawler_reclaimed 0
END

ngx_pagespeed memcached stats http://centminmod.com/nginx_ngx_pagespeed.html#stats

Code:

memcache_timeouts:                                                 0
memcache_last_error_checkpoint_ms:                     1403847998903
memcache_error_burst_size:                                         0
shm_cache_deletes:                                                 0
shm_cache_hits:                                               919477
shm_cache_inserts:                                              2770
shm_cache_misses:                                               2666
memcached_async_deletes:                                           0
memcached_async_hits:                                           2000
memcached_async_inserts:                                        2158
memcached_async_misses:                                         1819
memcached_blocking_deletes:                                        0
memcached_blocking_hits:                                        3842
memcached_blocking_inserts:                                    15894
memcached_blocking_misses:                                     31590

ngx_pagespeed histogram stats

 

it's web app or software dependent as explained at https://community.centminmod.com/threads/glory-or-fail.596/#post-2742 so ask the respective web app developer/support