[dtrace-discuss] cleanrate?

[Jon Haslam]

Hi Jim,

If you are seeing messages of the form "dtrace: 1234 speculative drops"
then you should (usually) try pushing the 'specsize' variable up to
increase the size of the speculative buffers - I think it's 32k by default.
'nspec' is used to control the number of buffers.

Whilst we are here, just a quick note on the cleaning rate tunable,
'cleanrate'. All the tunables which specify a frequency (cleanrate,
aggrate etc.) are actually assigned a value which when used as the
divisor of 1000000000 will give the desired frequency. Therefore to get
101hz the default value for cleanrate is 9900990 and you therefore need
to tune this down to increase the default frequency! I know this isn't
what the docs say w.r.t the cleanrate tunable.

Yes, this isn't actually user friendly. I don't know why it was done 
this way -
maybe one of the guys can comment on this.

Jon.

> I'm trying to avoid some drops from speculating and was trying to manipulate
> cleanrate to change the rate at which speculative buffers are processed (at least
> that's what I think it does).
>
> No matter what I set cleanrate to (even the default value of 101)
> I see the message: dtrace: cleaning rate reduced to 5000 hz.
>
> I am speculating at a fairly high rate and see lots of drops but if I 
> push nspec up too far, I see memory allocation failures or induce
> undesired side effects by consuming lots of system memory.
>
> Suggestions?
> --
> This message posted from opensolaris.org
> _______________________________________________
> dtrace-discuss mailing list
> dtrace-discuss at opensolaris.org
>