Re: [Qemu-devel] ideas for improving TLB performance (help with TCG backend wanted)

[Richard Henderson]

On 10/1/18 1:34 PM, Emilio G. Cota wrote:
> On Thu, Sep 20, 2018 at 01:19:51 +0100, Alex Bennée wrote:
>> If we are going to have an indirection then we can also drop the
>> requirement to scale the TLB according to the number of MMU indexes we
>> have to support. It's fairly wasteful when a bunch of them are almost
>> never used unless you are running stuff that uses them.
> 
> So with dynamic TLB sizing, what you're suggesting here is to resize
> each MMU array independently (depending on their use rate) instead
> of using a single "TLB size" for all MMU indexes. Am I understanding
> your point correctly?

You cannot do that without flushing the TBs (and with out-of-line memory ops,
the prologue as well) and regenerating.  The TLB size is baked into the code.
And we really don't have any extra registers free to vary that.


r~