I would appreciate if somebody can clarify a few points.
I am doing some random WRITES (100% writes, 100% random) testing and observe
that ARC grows way beyond the "hard" limit during the test. The hard
limit is set 512 MB via /etc/system and I see the size going up to 1 GB - how
come is it happening?
mdb''s ::memstat reports 1.5 GB used - does this include ARC as well or
is it separate?
I see on the backed only reads (205 MB/s) and almost no writes (1.1 MB/s) - any
ides what is being read?
--- BEFORE TEST
# ~/bin/arc_summary.pl
System Memory:
Physical RAM: 12270 MB
Free Memory : 7108 MB
LotsFree: 191 MB
ZFS Tunables (/etc/system):
set zfs:zfs_prefetch_disable = 1
set zfs:zfs_arc_max = 0x20000000
set zfs:zfs_arc_min = 0x10000000
ARC Size:
Current Size: 136 MB (arcsize)
Target Size (Adaptive): 512 MB (c)
Min Size (Hard Limit): 256 MB (zfs_arc_min)
Max Size (Hard Limit): 512 MB (zfs_arc_max)
...
> ::memstat
Page Summary Pages MB %Tot
------------ ---------------- ---------------- ----
Kernel 800895 3128 25%
ZFS File Data 394450 1540 13%
Anon 106813 417 3%
Exec and libs 4178 16 0%
Page cache 14333 55 0%
Free (cachelist) 22996 89 1%
Free (freelist) 1797511 7021 57%
Total 3141176 12270
Physical 3141175 12270
--- DURING THE TEST
# ~/bin/arc_summary.pl
System Memory:
Physical RAM: 12270 MB
Free Memory : 6687 MB
LotsFree: 191 MB
ZFS Tunables (/etc/system):
set zfs:zfs_prefetch_disable = 1
set zfs:zfs_arc_max = 0x20000000
set zfs:zfs_arc_min = 0x10000000
ARC Size:
Current Size: 1336 MB (arcsize)
Target Size (Adaptive): 512 MB (c)
Min Size (Hard Limit): 256 MB (zfs_arc_min)
Max Size (Hard Limit): 512 MB (zfs_arc_max)
ARC Size Breakdown:
Most Recently Used Cache Size: 87% 446 MB (p)
Most Frequently Used Cache Size: 12% 65 MB (c-p)
ARC Efficency:
Cache Access Total: 51681761
Cache Hit Ratio: 52% 27056475 [Defined State for
buffer]
Cache Miss Ratio: 47% 24625286 [Undefined State for
Buffer]
REAL Hit Ratio: 52% 27056475 [MRU/MFU Hits Only]
Data Demand Efficiency: 35%
Data Prefetch Efficiency: DISABLED (zfs_prefetch_disable)
CACHE HITS BY CACHE LIST:
Anon: --% Counter Rolled.
Most Recently Used: 13% 3627289 (mru) [ Return
Customer ]
Most Frequently Used: 86% 23429186 (mfu) [
Frequent Customer ]
Most Recently Used Ghost: 17% 4657584 (mru_ghost) [ Return
Customer Evicted, Now Back ]
Most Frequently Used Ghost: 32% 8712009 (mfu_ghost) [
Frequent Customer Evicted, Now Back ]
CACHE HITS BY DATA TYPE:
Demand Data: 30% 8308866
Prefetch Data: 0% 0
Demand Metadata: 69% 18747609
Prefetch Metadata: 0% 0
CACHE MISSES BY DATA TYPE:
Demand Data: 61% 15113029
Prefetch Data: 0% 0
Demand Metadata: 38% 9511898
Prefetch Metadata: 0% 359
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