Re: [PATCH v3] Weighted interleave auto-tuning

[Gregory Price <gourry@gourry.net>]

On Tue, Jan 21, 2025 at 07:17:15PM +0800, Huang, Ying wrote:
... snip ...
> 
> Unless it's possible we will add more modes in the future, this is kind
> of overkill for me.  How about something simpler as below?
> 
> $ cat auto
> true
> $ echo 0 > auto
> $ cat auto
> false

We have discussed having a dynamic-mode where the weights might adjust
on the fly based on system-state, but i think this ends up being
controlled under mempolicy/dynamic_interleave or something.

So this seems reasonable.

> >  static u8 __rcu *iw_table;
> >  static DEFINE_MUTEX(iw_table_lock);
> > +static const int weightiness = 32;
> > +static bool weighted_interleave_auto = true;
> 
> I still prefer to use 2 iw_table, one is for default, the other is for
> manual.  The default one will be used if the manual one is NULL.  Both
> are protected by RCU.  The default one can be updated upon hotplug
> blindly.  This makes the whole model easier to be understood IMHO.
> 
> What do you think about that.
> 

only question is, lets say you have

`cat auto node0 node1` -> `true 5 1`
and you do
echo 0 > auto

what should a subsequent `cat auto node0 node1` output?

`false 5 1`
or
`false 1 1`

Then lets say we do
echo 7 > node0

what should
echo true > auto
result in?

`true 5 1`
or
`true 7 1`

The current code makes sure that when you switch modes from auto
to manual, it inherits the current state - instead of there being
some hidden state that suddenly takes precedence.

So I prefer to just have one IW array and no hidden state.

~Gregory