[libvirt] [V2]RFC for support cache tune in libvirt

Martin Kletzander mkletzan at redhat.com
Mon Jan 9 13:09:34 UTC 2017


On Fri, Dec 23, 2016 at 05:38:13AM +0000, Qiao, Liyong wrote:
>
>Hi folks
>
>I’v send the V1 version RFC early this week, but no reply yet.
>

I replied to that and since I was going through the mail
chronologically, and this is not a reply to that one, I am getting to
this one only now.

>Thanks Qiaowei for the comment, I’v change the RFC much more libvirt specify, please help to comments on.
>
>##Propose Changes
>
>#Libvirtd configure changes
>
>Add a new configure option cache_allocation_ratio to libvirtd, which let libvirt to allocate how many cache to domains.
>

Where would be this option?  In libvirtd.conf?  Why?

>Default is 0.5
>
>Eg.
>On a host which has 55M cache, libvirt can allocate 55M * cache_allocation_ratio cache to domains
>

Why does this have to be statically limited?

>## Virsh command line changes:
>
> NAME
>   cachetune - control or query domain cache allocation
>
> SYNOPSIS
>   cachetune <domain> [--enabled true/false] [--type <type>][--size <number>] [--config] [--live] [--current]
>
> DESCRIPTION
>   Allocate cache usage for domain.
>
> OPTIONS
>   [--domain] <string>  domain name, id or uuid
>   --enabled <true/false>  enable cache allocation

So if I want to clear it out, I do "cachetune --enable false"?  That's a
mouthful.

>   --type <string>  cache allocations type, support l3/l2 etc
>   --size <number> the cache size in KB
>   --config         affect next boot
>   --live           affect running domain
>   --current        affect current domain
>
>This will allow libvirt to allocate specify type l3 cache for a domain
>
>Domain xml changes:
>
><cachetune>
><enabled=’yes’, size=4096, actual_size=4680,type=’l3’>
><enabled=’no’, size=256, actual_size=0, type=’l2’>
></cachetune>
>

<cachetune> sounds fine, but the rest... enabled=no doesn't make sense,
same as actual_size=0, but I guess that's just the same thing.  It's
also missing code/data differentiation.  And socket/vCPU information.

>
>For more information about the detail design, please refer https://www.redhat.com/archives/libvir-list/2016-December/msg01011.html
>
>CAT intro: https://software.intel.com/en-us/articles/software-enabling-for-cache-allocation-technology
>
>
>
>Best Regards
>
>Eli Qiao(乔立勇)OpenStack Core team OTC Intel.
>--
>

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