ARC size limit

[Steven Hartland]

You need https://svnweb.freebsd.org/base?view=revision&revision=272875
On 04/11/2014 06:29, George Kola wrote:
> Hi All,
>         This is my first post to freebsd-stable fresh of Meet BSD California 2014.  We are switching our entire production to FreeBSD. Our storage servers have  256 GB of RAM , 4 TB of SSD and 40 TB of spinning disks. We are running ZFS root and the SSD is configured as L2ARC.  We are running FreeBSD 10.1 RC3
>         I am finding that on all our machines, ARC is somehow limited to < 64 GB of memory and we have a huge inactive memory (180 G). The surprising thing is that ARC seems to have almost the same limit  (< 64 GB) on all of our storage boxes and ARC is not growing even though L2ARC hit shows that there is advantage in growing ARC.
>         Any help/pointers is appreciated.
>         What I am trying to do is to tune ZFS for our workload. We are hoping that we get a high hit rate.
>         Thanks to Justin Gibbs and Allan Jude for initial pointers and help. They suggested posting to the mailing list to get further help.
>
>         I have pasted top output and zfs-stats output below and yes UMA is enabled.
>
> Thanks,
> George
>         
>
>
> top
> last pid: 27458;  load averages:  3.30,  5.42,  5.34                                                                                                up 6+09:59:30  05:38:49
> 71 processes:  1 running, 70 sleeping
> CPU:  4.2% user,  0.0% nice,  4.6% system,  0.2% interrupt, 90.9% idle
> Mem: 11G Active, 181G Inact, 52G Wired, 1368M Cache, 4266M Free
> ARC: 47G Total, 1555M MFU, 41G MRU, 35M Anon, 3984M Header, 709M Other
> Swap: 64G Total, 2874M Used, 61G Free, 4% Inuse
>
>
>
> sysctl vfs.zfs.zio.use_uma
> vfs.zfs.zio.use_uma: 1
>
>
>
>
> zfs-mon -a output
>
> ZFS real-time cache activity monitor
> Seconds elapsed:  62
>
> Cache hits and misses:
>                                    1s    10s    60s    tot
>                       ARC hits:   124    126    103    101
>                     ARC misses:    35     46     29     28
>           ARC demand data hits:    55     90     61     61
>         ARC demand data misses:    20     32     18     17
>       ARC demand metadata hits:    69     36     42     40
>     ARC demand metadata misses:     9     13     10      9
>         ARC prefetch data hits:     0      0      0      0
>       ARC prefetch data misses:     6      1      1      1
>     ARC prefetch metadata hits:     0      0      0      0
>   ARC prefetch metadata misses:     0      0      0      0
>                     L2ARC hits:    16     28     14     14
>                   L2ARC misses:    19     18     15     14
>                    ZFETCH hits:   592   2842   2098   2047
>                  ZFETCH misses:   308   1326    507    494
>
> Cache efficiency percentage:
>                            10s    60s    tot
>                    ARC:  73.26  78.03  78.29
>        ARC demand data:  73.77  77.22  78.21
>    ARC demand metadata:  73.47  80.77  81.63
>      ARC prefetch data:   0.00   0.00   0.00
> ARC prefetch metadata:   0.00   0.00   0.00
>                  L2ARC:  60.87  48.28  50.00
>                 ZFETCH:  68.19  80.54  80.56
>
>
>
>
> zfs-stats -a output
>
> ZFS real-time cache activity monitor
> Seconds elapsed:  62
>
> Cache hits and misses:
>                                    1s    10s    60s    tot
>                       ARC hits:   124    126    103    101
>                     ARC misses:    35     46     29     28
>           ARC demand data hits:    55     90     61     61
>         ARC demand data misses:    20     32     18     17
>       ARC demand metadata hits:    69     36     42     40
>     ARC demand metadata misses:     9     13     10      9
>         ARC prefetch data hits:     0      0      0      0
>       ARC prefetch data misses:     6      1      1      1
>     ARC prefetch metadata hits:     0      0      0      0
>   ARC prefetch metadata misses:     0      0      0      0
>                     L2ARC hits:    16     28     14     14
>                   L2ARC misses:    19     18     15     14
>                    ZFETCH hits:   592   2842   2098   2047
>                  ZFETCH misses:   308   1326    507    494
>
> Cache efficiency percentage:
>                            10s    60s    tot
>                    ARC:  73.26  78.03  78.29
>        ARC demand data:  73.77  77.22  78.21
>    ARC demand metadata:  73.47  80.77  81.63
>      ARC prefetch data:   0.00   0.00   0.00
> ARC prefetch metadata:   0.00   0.00   0.00
>                  L2ARC:  60.87  48.28  50.00
>                 ZFETCH:  68.19  80.54  80.56
>
>
>
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