ARC & L2ARC efficiency

[Artem Belevich]

There's a pretty useful script to present ARC stats (alas, L2ARC info
is not included) in a readable way:
http://cuddletech.com/arc_summary/

I've attaches somewhat hacked (and a bit outdated) version that runs on FreeBSD.

--Artem



On Thu, Oct 1, 2009 at 1:22 PM, Alexander Shevchenko <pepelac at gmail.com> wrote:
> Good time of day!
>
> How could i check the efficiency of ARC?
> Are total reads from pool equal kstat.zfs.misc.arcstats.hits +
> kstat.zfs.misc.arcstats.misses, or this values are just reads from cache?
> By  efficiency i mean reads_from_cache/(reads_from_cache+reads_from_drives)
> Are there any document where kstat values described?
>
> zpool status
>  pool: data
>  state: ONLINE
>  scrub: none requested
> config:
>
>        NAME        STATE     READ WRITE CKSUM
>        data        ONLINE       0     0     0
>          da2       ONLINE       0     0     0
>          da4       ONLINE       0     0     0
>        cache
>          da3       ONLINE       0     0     0
>
>
> #sysctl kstat
> kstat.zfs.misc.arcstats.hits: 282927703
> kstat.zfs.misc.arcstats.misses: 66220328
> kstat.zfs.misc.arcstats.demand_data_hits: 164374119
> kstat.zfs.misc.arcstats.demand_data_misses: 6615511
> kstat.zfs.misc.arcstats.demand_metadata_hits: 88715021
> kstat.zfs.misc.arcstats.demand_metadata_misses: 4464890
> kstat.zfs.misc.arcstats.prefetch_data_hits: 28851210
> kstat.zfs.misc.arcstats.prefetch_data_misses: 55109950
> kstat.zfs.misc.arcstats.prefetch_metadata_hits: 987353
> kstat.zfs.misc.arcstats.prefetch_metadata_misses: 29977
> kstat.zfs.misc.arcstats.mru_hits: 44560461
> kstat.zfs.misc.arcstats.mru_ghost_hits: 1493532
> kstat.zfs.misc.arcstats.mfu_hits: 211027800
> kstat.zfs.misc.arcstats.mfu_ghost_hits: 16337660
> kstat.zfs.misc.arcstats.deleted: 49112923
> kstat.zfs.misc.arcstats.recycle_miss: 9574100
> kstat.zfs.misc.arcstats.mutex_miss: 252423
> kstat.zfs.misc.arcstats.evict_skip: 2269320648
> kstat.zfs.misc.arcstats.hash_elements: 644877
> kstat.zfs.misc.arcstats.hash_elements_max: 678888
> kstat.zfs.misc.arcstats.hash_collisions: 21697862
> kstat.zfs.misc.arcstats.hash_chains: 182323
> kstat.zfs.misc.arcstats.hash_chain_max: 9
> kstat.zfs.misc.arcstats.p: 1251375616
> kstat.zfs.misc.arcstats.c: 1252817408
> kstat.zfs.misc.arcstats.c_min: 1252817408
> kstat.zfs.misc.arcstats.c_max: 10022539264
> kstat.zfs.misc.arcstats.size: 1237578176
> kstat.zfs.misc.arcstats.hdr_size: 9610640
> kstat.zfs.misc.arcstats.l2_hits: 12905801
> kstat.zfs.misc.arcstats.l2_misses: 680
> kstat.zfs.misc.arcstats.l2_feeds: 52666
> kstat.zfs.misc.arcstats.l2_rw_clash: 680
> kstat.zfs.misc.arcstats.l2_writes_sent: 41330
> kstat.zfs.misc.arcstats.l2_writes_done: 41330
> kstat.zfs.misc.arcstats.l2_writes_error: 0
> kstat.zfs.misc.arcstats.l2_writes_hdr_miss: 62
> kstat.zfs.misc.arcstats.l2_evict_lock_retry: 53
> kstat.zfs.misc.arcstats.l2_evict_reading: 5
> kstat.zfs.misc.arcstats.l2_free_on_write: 30044
> kstat.zfs.misc.arcstats.l2_abort_lowmem: 309837
> kstat.zfs.misc.arcstats.l2_cksum_bad: 0
> kstat.zfs.misc.arcstats.l2_io_error: 0
> kstat.zfs.misc.arcstats.l2_size: 79319831552
> kstat.zfs.misc.arcstats.l2_hdr_size: 134102528
> kstat.zfs.misc.arcstats.memory_throttle_count: 112340
> kstat.zfs.misc.vdev_cache_stats.delegations: 3822
> kstat.zfs.misc.vdev_cache_stats.hits: 342974
> kstat.zfs.misc.vdev_cache_stats.misses: 170601
>
>
> WBR,
> Alexander Shevchenko
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