[ubuntu-uk] Ubuntu unusably slow

[Colin Law]

On 7 February 2013 14:18, Alan Pope <alan.pope at canonical.com> wrote:
> On 07/02/13 12:47, Gareth France wrote:
>>
>> I've just had a peek and apparently it's using swap memory right now!
>> Memory 1.5Gb of 3.5Gb used
>> Swap 658.9Mb of 3.7Gb used
>>
>
> Using swap is not a problem. Swapping is the problem.

It is unusual though to see half a gig in swap when less than half of
the RAM is is use, is it not?  For example mine has been on all day
and is still showing zero swap (I have 4GB RAM).  Does it not mean
that at some point something has been using a lot?

Colin

>
> Using swap just means there's a chunk of space on disk which is set aside to
> swap stuff into, or stuff has been swapped into it.
>
> Swapping is the act of throwing stuff out to disk or pulling stuff in.
> Intensive swapping will slow the machine down and cause things to become
> very sluggish.
>
> I would open a terminal (as others have suggested) and have it running
> "vmstat 5" which will print a line every 5 seconds like this:-
>
> rocs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
>  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id
> wa
>  1  0 894156 2244868  50860 1636816    6   12   945    66   60  164 23  5 72
> 0
>  0  0 894152 2242432  50876 1637120    6    0     6    39 1047 3910 11  2 87
> 0
>  2  0 894148 2247616  50884 1637184    0    0     6    35  980 3671  9  2 88
> 0
>  0  0 894148 2247588  50900 1637184    0    0     0    65  939 3379  8  2 90
> 0
>  0  0 894148 2247260  50908 1636908    0    0     0    12  834 3111  7  2 91
> 0
>  0  0 894148 2185816  50928 1698776    0    0     0   147 1093 4012 11  2 88
> 0
>
>
>
> Ignore the first line, but when things go bad you'll see the numbers change.
> The "si" and "so" columns indicate swapping, if they're repeatedly non-zero
> then you're doing some swapping. "bi" and "bo" can mean just general disk IO
> (like the normal stuff applications do). "us" is cpu time spent running
> applications and "sy" is system time. You may also see high "cs" (context
> switches) as the processor is under load, flipping between one task and
> another, and rarely getting any real work done.
>
> vmstat and top are very good for diagnosing this stuff, don't bother with
> gui tools, they just make it worse :)
>
>
> Cheers,
> --
> Alan Pope
> Engineering Manager
>
> Canonical - Product Strategy
> +44 (0) 7973 620 164
> alan.pope at canonical.com
> http://ubuntu.com/
>
> --
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