[OpenIndiana-discuss] Question about System Monitor

Thu Jul 8 14:54:51 UTC 2021

Because of the way swap is implemented on Solaris and descendants (on SVR4 in general, maybe), the vmstat "swap" column is very misleading; check output of swap -l (lower-case L option) instead, and if the free column is the same as the blocks column, no real swap is actually being used.

Likewise, all block disk I/O (including filesystem) goes though the paging mechanism, so the vmstat "pi" column just reflects reads or access via mmap. Given that the "po" column is zero, I doubt that you're actually paging out just to make room, although that's not a great indication, as file or block disk writes or pages written due to msync() would also probably count there.

I suspect some of the misleading "swap" column change may also be due to files being created and written, or deleted, in tmpfs filesystems like /tmp and /var/run.

> On Jul 8, 2021, at 10:40, russell <stream at willows7.myzen.co.uk> wrote:
> 
> Hi,
> 
> I am running Hipster 2021.04 with illumos-3f770aab81 and running System Monitor 1.24.2.
> System monitor is reporting Memory utilisation of 17.5GiB (27.5%) of 63.9GiB, however it is reporting 115.7MiB (0.7%) of 15.9GiB of swap it being used.
> I have always thought that swapping occurred when there is insufficient memory for an application so another application or pages of an application could be swapped to disk to free RAM.
> Given that there at least 32GB of RAM free, surely it would not need to page.
> 
> $ vmstat 30
>  kthr      memory                             page disk                          faults      cpu
>  r b w    swap          free       re   mf    pi po   fr de sr ro   s0 s1 s2   in       sy           cs   us sy id
>  0 0 0 68532576 60872200 33 244   41 0  0   0  55   8   4   4 -0   4516   11765  6689    1 0 99
>  0 0 0 49794916 48173452 1   431 344 0  0   0    0 49 23 25   0 18812 119079 53181   9 3 88
>  0 0 0 49782568 48159484 2   725 300 0  0   0    0 32 16 17   0 16908 121531 53655 10 3 87
>  0 0 0 49762892 48139892 0   754 218 0  0   0    0 33 17 17   0 20269 118644 52612 10 3 87
>  0 0 0 49735940 48112244 3   595 407 0  0   0    0 54 28 27   0 19599 119165 53390 10 3 87
>  0 0 0 49712360 48086132 2   476 244 0  0   0    0 37 19 19   0 19248 119117 53090 10 3 87
>  0 0 0 49692084 48064828 17 444 435 0  0   0    0 43 22 21   0 19950 119938 53753 10 3 87
> 
> While it is only around 100MB can I tweak the system to avoid paging when there is so much ram?
> 
> TIA
> 
> Russell
> 
> 
> 
> 
> _______________________________________________
> openindiana-discuss mailing list
> openindiana-discuss at openindiana.org
> https://openindiana.org/mailman/listinfo/openindiana-discuss
> 