Hi,

we are trying to implement better memcached monitoring and have come
across this problem with 1.4.5:

- after flush_all on a filled (long-running) memcached, we get
evictions immediately (within seconds, none of the buckets should fill
up that quickly)

This would mean that either flushed items count toward evictions when
replaced (even though they should not be valid items after flush_all
and evictions should count only valid items that were replaced) or
that somehow flush_all does not work as expected, or that we have a
pathetically bad distribution of item sizes and memcached will not
reallocate slabs/buckets after a flush_all(?).

If this behaviour is normal, does anyone have a better suggestion
regarding what to monitor other than evictions to see if more
memcached instances would be needed?

Memcached options were:

memcached -v -m 2000 -l 10.0.0.22 -p 11211 -u root

stats items reports evictions (shortly after flushing) in 2 buckets:

STAT items:5:number 8737
STAT items:5:age 24656
STAT items:5:evicted 16
STAT items:5:evicted_nonzero 0
STAT items:5:evicted_time 130774
STAT items:5:outofmemory 0
STAT items:5:tailrepairs 0
STAT items:5:reclaimed 6

STAT items:19:number 8832
STAT items:19:age 141322
STAT items:19:evicted 45
STAT items:19:evicted_nonzero 45
STAT items:19:evicted_time 14103
STAT items:19:outofmemory 0
STAT items:19:tailrepairs 0
STAT items:19:reclaimed 8

stats slabs:

STAT 5:chunk_size 240
STAT 5:chunks_per_page 4369
STAT 5:total_pages 2
STAT 5:total_chunks 8738
STAT 5:used_chunks 8738
STAT 5:free_chunks 0
STAT 5:free_chunks_end 0
STAT 5:mem_requested 1826616
STAT 5:get_hits 0
STAT 5:cmd_set 226
STAT 5:delete_hits 0
STAT 5:incr_hits 0
STAT 5:decr_hits 0
STAT 5:cas_hits 0
STAT 5:cas_badval 0

STAT 19:chunk_size 5680
STAT 19:chunks_per_page 184
STAT 19:total_pages 48
STAT 19:total_chunks 8832
STAT 19:used_chunks 8832
STAT 19:free_chunks 0
STAT 19:free_chunks_end 0
STAT 19:mem_requested 42671558
STAT 19:get_hits 17
STAT 19:cmd_set 217
STAT 19:delete_hits 0
STAT 19:incr_hits 0
STAT 19:decr_hits 0
STAT 19:cas_hits 0
STAT 19:cas_badval 0

Thanks,
 Marinos

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