Re: RCU red-black tree (was: Re: [PATCH 4/6] kvm tools: Add rwlock wrapper)

Prasad Joshi
2011-05-31T19:09:32Z

On Tue, May 31, 2011 at 4:25 PM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Sasha Levin <levinsasha928@gmail.com> wrote:
>
>> On Tue, 2011-05-31 at 15:09 +0200, Ingo Molnar wrote:
>> > * Sasha Levin <levinsasha928@gmail.com> wrote:
>> >
>> > > I've started working on converting our MMIO code to use RCU rbtree.
>> >
>> > Well, why would we want to switch the MMIO code away from the brlock
>> > right now? mmio tree reconfigurations are very, very rare.
>> >
>> > Won't something like the qcow cache be more suitable for that? That
>> > has both frequent read and write activities.
>>
>> We don't have a qcow cache at the moment :)
>
> Wasnt one in the works by Prasad?

I have the code changes which work. I think I had send patches few
days back as well there were few improvements. The only reason I did
not send the v2 of the patch is, I am not seeing performance
improvement by adding cache.

May be the DD of 1G file was a wrong test to calculate the
performance. Sasha had asked me to run boniee++ for performance
numbers. I will ensure the patches can be applied on the latest code
base and send the patches. Sorry for the delay.

Thanks and Regards,
Prasad

>
>> It was either the MMIO or the ioport tree. We don't have to pull
>> them into our master tree either - it's mostly a proof of concept
>> I'm doing on a separate tree.
>
> Sure.
>
> Thanks,
>
>        Ingo
>