Re: [Xen-API] [Squeezd] Disabling some balancing features

[Dave Scott <Dave.Scott@xxxxxxxxxxxxx>]

Hi,

Kakadu wrote:

> Hey.
> 
> I have accepted a challenge about disabling some features of
> automatical rebalancing. For example, I want squeezed to raise an
> exception while migration in case if there is not enough free memory
> and some squeezing needed. So I fixed reserve-memory handler in my
> squeezed-like daemon [1] and implemented successful result only when
> we can get needed memory without squeezing [2].
> 
> My big problem is testing that stuff. I have vm with these
> characteristics
> $ xe vm-param-list uuid=ec1dec56-ae4f-d854-8065-e106a1139361 | grep
> memory
>                  memory-actual ( RO): 250609664
>                  memory-target ( RO): 250609664
>                memory-overhead ( RO): 4194304
>              memory-static-max ( RW): 250000000
>             memory-dynamic-max ( RW): 250000000
>             memory-dynamic-min ( RW): 250000000
>              memory-static-min ( RW): 250000000
> 
> and while localhost migration Squeezer says that it can't  reserve
> memory without squeezing.
> 
> [20121019T14:36:28.830Z|debug|xenhost-1|0|reserve_memory(xapi,
> 256428)|xenstore-rpc] using new version of reserve_memory
> [20121019T14:36:28.830Z|debug|xenhost-1|0|reserve_memory(xapi,
> 256428)|xenops] force_change_host_free_memory required_mem = 265644
> KiB
> [20121019T14:36:28.831Z|debug|xenhost-1|0|reserve_memory(xapi,
> 256428)|xenops] Total non-domain reservations = 811008
> [20121019T14:36:28.831Z|debug|xenhost-1|0|reserve_memory(xapi,
> 256428)|xenops] domid 3 has been declared inactive
> [20121019T14:36:28.831Z|debug|xenhost-1|0|reserve_memory(xapi,
> 256428)|xenops] total_range = 0 gamma = 1.000000 gamma' = inf
> [20121019T14:36:28.831Z|debug|xenhost-1|0|reserve_memory(xapi,
> 256428)|xenops] Total additional memory over dynamic_min = 2675808
> KiB; will set gamma = 1.00 (leaving unallocated 0 KiB)
> [20121019T14:36:28.831Z|debug|xenhost-1|0|reserve_memory(xapi,
> 256428)|xenops] Maximum possible free memory if all active domains
> balloon down to dynamic_min = 2941452
> [20121019T14:36:28.831Z|debug|xenhost-1|0|reserve_memory(xapi,
> 256428)|xenops] current host free mem = 2941452 KiB (aiming for 265644
> KiB); OK; all domain targets not reached; allocation phase
> [20121019T14:36:28.831Z|debug|xenhost-1|0|reserve_memory(xapi,
> 256428)|xenops] Can't free 265644 KiB: some domains need squeezing
> 
> I'm a little bit confused why first number is less than second in `
> mem = 2941452 KiB (aiming for 265644 KiB)`. Maybe I dont understand
> something good enough

I think what it's trying to say is:

The host has 2.9 GiB free but we'd like to give most of this free memory away 
to domains (by 'balancing'), to leave only 265644 KiB left.

> So I have two questions:
> 1) How to setup parameters for testing migration with my new daemon?
> 2) What else pifalls I will have in my way while disabling
> autobalancing?

When you try to migrate to a host which hasn't got much free memory, do you 
intend to run the existing squeezing logic?

BTW there is some internal squeezed design documentation here, just in case its 
useful:

https://github.com/xen-org/xen-api/tree/master/docs/squeezed

Cheers,
Dave

> 
> 
> Cheers,
> Kakadu
> 
> [1] https://github.com/Kakadu/xcp-xapi/blob/master/debian/patches/0101-
> serred.patch#L123
> [2] https://github.com/Kakadu/xcp-xapi/blob/master/debian/patches/0101-
> serred.patch#L617
> 
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