Unexpected zfs ARC behavior
Steven Hartland
killing at multiplay.co.uk
Sun Sep 28 14:26:36 UTC 2014
I wouldn't expect that to be related tbh.
----- Original Message -----
From: "FF" <fusionfoto at gmail.com>
To: <freebsd-fs at freebsd.org>
Sent: Sunday, September 28, 2014 10:00 AM
Subject: Re: Unexpected zfs ARC behavior
> I'm not sure, but this may be addressed by :
>
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=191510.
>
> On the same system, on a brand new SSD (Intel 320 series, supports TRIM,
> 973 hours of total run time and no SMARTCTL errors), the l2arc is accruing
> some errors and I can't tell if they are inter-related or not.
>
> sysctl -a |grep l2_
> kstat.zfs.misc.arcstats.evict_l2_cached: 8717673244160
> kstat.zfs.misc.arcstats.evict_l2_eligible: 2307662193664
> kstat.zfs.misc.arcstats.evict_l2_ineligible: 3432677600768
> kstat.zfs.misc.arcstats.l2_hits: 11990587
> kstat.zfs.misc.arcstats.l2_misses: 66503164
> kstat.zfs.misc.arcstats.l2_feeds: 3721611
> kstat.zfs.misc.arcstats.l2_rw_clash: 153
> kstat.zfs.misc.arcstats.l2_read_bytes: 1152794672128
> kstat.zfs.misc.arcstats.l2_write_bytes: 27096209368064
> kstat.zfs.misc.arcstats.l2_writes_sent: 1741090
> kstat.zfs.misc.arcstats.l2_writes_done: 1741090
> kstat.zfs.misc.arcstats.l2_writes_error: 0
> kstat.zfs.misc.arcstats.l2_writes_hdr_miss: 2479
> kstat.zfs.misc.arcstats.l2_evict_lock_retry: 1149
> kstat.zfs.misc.arcstats.l2_evict_reading: 137
> kstat.zfs.misc.arcstats.l2_free_on_write: 1000507
> kstat.zfs.misc.arcstats.l2_abort_lowmem: 225
> kstat.zfs.misc.arcstats.l2_cksum_bad: 8
> kstat.zfs.misc.arcstats.l2_io_error: 6
> kstat.zfs.misc.arcstats.l2_size: 35261600768
> kstat.zfs.misc.arcstats.l2_asize: 33760987648
> kstat.zfs.misc.arcstats.l2_hdr_size: 58288928
> kstat.zfs.misc.arcstats.l2_compress_successes: 31952645
> kstat.zfs.misc.arcstats.l2_compress_zeros: 903
> kstat.zfs.misc.arcstats.l2_compress_failures: 436119
> kstat.zfs.misc.arcstats.l2_write_trylock_fail: 2481253
> kstat.zfs.misc.arcstats.l2_write_passed_headroom: 61954692
> kstat.zfs.misc.arcstats.l2_write_spa_mismatch: 26664326
> kstat.zfs.misc.arcstats.l2_write_in_l2: 19967700467
> kstat.zfs.misc.arcstats.l2_write_io_in_progress: 94722
> kstat.zfs.misc.arcstats.l2_write_not_cacheable: 11359575294
> kstat.zfs.misc.arcstats.l2_write_full: 730445
> kstat.zfs.misc.arcstats.l2_write_buffer_iter: 3721611
> kstat.zfs.misc.arcstats.l2_write_pios: 1741090
> kstat.zfs.misc.arcstats.l2_write_buffer_bytes_scanned: 3464594001047552
> kstat.zfs.misc.arcstats.l2_write_buffer_list_iter: 229359623
> kstat.zfs.misc.arcstats.l2_write_buffer_list_null_iter: 65007815
>
>
> Anyway, thanks in advance for any help offered.
>
> Best.
>
>
> On Sat, Sep 27, 2014 at 2:24 PM, FF <fusionfoto at gmail.com> wrote:
>
>>
>> Hi, forwarding from -questions.
>>
>> It looks like the image didn't make it across, so here it is:
>>
>> http://snag.gy/Ghb7X.jpg
>>
>> Thanks in advance for any pointers or suggestions, or confirmations that
>> somehow this behavior is normal.
>>
>> --
>>
>>
>> So on a somewhat loaded ZFS file server (all NFS) serving mostly VMs with
>> the load steadily increasing over the month (migrated from other
>> servers)... the ARC size has unexpectedly dropped (please see attached
>> graphic, if it makes through the mailing list server). The system peaks
>> around 2,000 NFS IOPS and hasn't exhibited any slow downs. The L2ARC has a
>> very low hit rate and prefetch has been turned off to increase the L2ARC
>> efficiency... but none of that should really matter as far as I can tell
>> since the L1ARC should try to use all the memory it can.
>>
>>>
>>> Some tuning of zfs sysctls (mostly write_boost and write_max) to increase
>>> them, but this has since been backed off to default.
>>>
>>> vmstat -m reports that 24G is dedicated to opensolaris:
>>> solaris 1113433 24565820K - 6185559839
>>> 16,32,64,128,256,512,1024,2048,4096
>>>
>>> And top reports memory free:
>>>
>>> last pid: 32075; load averages: 0.16, 0.13,
>>> 0.14 up 36+21:44:59 09:16:49
>>> 24 processes: 1 running, 23 sleeping
>>> CPU: 0.0% user, 0.0% nice, 0.0% system, 0.6% interrupt, 99.4% idle
>>> Mem: 25M Active, 1187M Inact, 26G Wired, 2048K Cache, 1536M Buf, 4160M
>>> Free
>>> ARC: 14G Total, 1679M MFU, 12G MRU, 28M Anon, 156M Header, 21M Other
>>>
>>> zfs-stats -a :
>>>
>>> ------------------------------------------------------------------------
>>> ZFS Subsystem Report Sat Sep 27 09:17:07 2014
>>> ------------------------------------------------------------------------
>>>
>>> System Information:
>>>
>>> Kernel Version: 902001 (osreldate)
>>> Hardware Platform: amd64
>>> Processor Architecture: amd64
>>>
>>> ZFS Storage pool Version: 5000
>>> ZFS Filesystem Version: 5
>>>
>>> FreeBSD 9.2-RELEASE-p10 #0 r270148M: Mon Aug 18 23:14:36 EDT 2014 root
>>> 9:17AM up 36 days, 21:45, 2 users, load averages: 0.12, 0.12, 0.13
>>>
>>> ------------------------------------------------------------------------
>>>
>>> System Memory:
>>>
>>> 0.08% 26.22 MiB Active, 3.75% 1.16 GiB Inact
>>> 82.36% 25.47 GiB Wired, 0.01% 2.00 MiB Cache
>>> 13.80% 4.27 GiB Free, 0.00% 1.03 MiB Gap
>>>
>>> Real Installed: 32.00 GiB
>>> Real Available: 99.63% 31.88 GiB
>>> Real Managed: 97.01% 30.93 GiB
>>>
>>> Logical Total: 32.00 GiB
>>> Logical Used: 83.03% 26.57 GiB
>>> Logical Free: 16.97% 5.43 GiB
>>>
>>> Kernel Memory: 23.54 GiB
>>> Data: 99.90% 23.52 GiB
>>> Text: 0.10% 23.13 MiB
>>>
>>> Kernel Memory Map: 29.76 GiB
>>> Size: 76.40% 22.74 GiB
>>> Free: 23.60% 7.02 GiB
>>>
>>> ------------------------------------------------------------------------
>>>
>>> ARC Summary: (HEALTHY)
>>> Memory Throttle Count: 0
>>>
>>> ARC Misc:
>>> Deleted: 90.09m
>>> Recycle Misses: 2.44m
>>> Mutex Misses: 794.67k
>>> Evict Skips: 17.90m
>>>
>>> ARC Size: 44.78% 13.40 GiB
>>> Target Size: (Adaptive) 44.78% 13.40 GiB
>>> Min Size (Hard Limit): 12.50% 3.74 GiB
>>> Max Size (High Water): 8:1 29.93 GiB
>>>
>>> ARC Size Breakdown:
>>> Recently Used Cache Size: 86.16% 11.55 GiB
>>> Frequently Used Cache Size: 13.84% 1.85 GiB
>>>
>>> ARC Hash Breakdown:
>>> Elements Max: 786.71k
>>> Elements Current: 87.05% 684.85k
>>> Collisions: 153.35m
>>> Chain Max: 16
>>> Chains: 194.92k
>>>
>>> ------------------------------------------------------------------------
>>>
>>> ARC Efficiency: 506.24m
>>> Cache Hit Ratio: 87.56% 443.25m
>>> Cache Miss Ratio: 12.44% 62.99m
>>> Actual Hit Ratio: 80.06% 405.29m
>>>
>>> Data Demand Efficiency: 93.92% 372.74m
>>> Data Prefetch Efficiency: 49.49% 69.76m
>>>
>>> CACHE HITS BY CACHE LIST:
>>> Anonymously Used: 6.10% 27.05m
>>> Most Recently Used: 31.37% 139.05m
>>> Most Frequently Used: 60.07% 266.24m
>>> Most Recently Used Ghost: 0.80% 3.56m
>>> Most Frequently Used Ghost: 1.66% 7.35m
>>>
>>> CACHE HITS BY DATA TYPE:
>>> Demand Data: 78.98% 350.09m
>>> Prefetch Data: 7.79% 34.53m
>>> Demand Metadata: 12.15% 53.86m
>>> Prefetch Metadata: 1.08% 4.77m
>>>
>>> CACHE MISSES BY DATA TYPE:
>>> Demand Data: 35.95% 22.65m
>>> Prefetch Data: 55.93% 35.23m
>>> Demand Metadata: 4.49% 2.83m
>>> Prefetch Metadata: 3.63% 2.29m
>>>
>>> ------------------------------------------------------------------------
>>> <cut>
>>>
>>> Any suggestions? Is this expected or acceptable behavior?
>>>
>>> Thanks in advance,
>>>
>>> --
>>> FF
>>>
>>
>>
>>
>> --
>> FF
>>
>
>
>
> --
> FF
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