vmstat -z: zfs related failures on r255173

[Dmitriy Makarov]

Please, any idea, thougth, help! 
Maybe what information can be useful for diggin - anything...

System what I'm talkin about has a huge problem: performance degradation in short time period (day-two). Don't know can we somehow relate this vmstat fails with degradation.


 
> Hi all
> 
> On CURRENT r255173 we have some interesting values from vmstat -z : REQ = FAIL
> 
> [server]# vmstat -z
> ITEM                   SIZE  LIMIT     USED     FREE      REQ FAIL SLEEP
> ....... skipped....
> NCLNODE:                528,      0,       0,       0,       0,   0,   0
> space_seg_cache:         64,      0,  289198,  299554,25932081,25932081,   0
> zio_cache:              944,      0,   37512,   50124,1638254119,1638254119,   0
> zio_link_cache:          48,      0,   50955,   38104,1306418638,1306418638,   0
> sa_cache:                80,      0,   63694,      56,  198643,198643,   0
> dnode_t:                864,      0,  128813,       3,  184863,184863,   0
> dmu_buf_impl_t:         224,      0, 1610024,  314631,157119686,157119686,   0
> arc_buf_hdr_t:          216,      0,82949975,   56107,156352659,156352659,   0
> arc_buf_t:               72,      0, 1586866,  314374,158076670,158076670,   0
> zil_lwb_cache:          192,      0,    6354,    7526, 2486242,2486242,   0
> zfs_znode_cache:        368,      0,   63694,      16,  198643,198643,   0
> ..... skipped ......
> 
> Can anybody explain this strange failures in zfs related parameters in vmstat, can we do something with this and is this really bad signal?
> 
> Thanks!