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

[Qiao, Liyong]

Hi Martin,

Thanks for your comments, it’s really helpful, I’v changed some of the design and with some PoC code.
And will later sent the v3 version of cachetune for libvirt, will add you in CC list.

I have some PoC code based on 3.0.0, not finished yet. But I’v learned that 3.0.0 will be released soon, seems there will be some rebase work to do.


Best Regards

Eli Qiao(乔立勇）OpenStack Core team OTC Intel.
-- 


On 09/01/2017, 9:09 PM, "Martin Kletzander" <mkletzan at redhat.com> wrote:

    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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