Re: TLB tiredown by ASID bump

["Toru Nishimura" <locore64%alkyltechnology.com@localhost>]

Matt Thomas made a comment;

> The ASID generational stuff has a downside in that valid 
> entries will be thrown away.  For mips (and booke) I use
> a different algorithm which eliminates the overhead of
> discarding all the TLB entries when you run out of ASIDs.

It's a good move to pursue efficent ASID management
schemes since it's the key area for runtime VM/TLB activity.

Matt points loosing valid entries is a problem when ASID
generation is going to get bumped.  I think, however, it'd be
forgiven that tbia() operation, to discard all entries but global
or locked, discards "live entries" since TLB size is still small
enough.  Some CPU architectures do it  with a single
special instruction or others do at-most 64 time loop to discard.
TLB is a cache for VA->PA translation and the management
scheme always provokes "efficiency v.s. correctness"
arguments.  It's a matter of implementation tradeoff, I believe.

BTW, how do you approach to implement a remote TLB
shootdown?

Toru Nishimura / ALKYL Technology