Re: [Qemu-devel] [PATCH v2 2/3] migration: Dynamic cpu throttling for auto-converge

[Eric Blake <eblake@redhat.com>]

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On 06/02/2015 11:46 AM, Jason J. Herne wrote:
> Remove traditional auto-converge static 30ms throttling code and replace it
> with a dynamic throttling algorithm.
> 
> Additionally, be more aggressive when deciding when to start throttling.
> Previously we waited until four unproductive memory passes. Now we begin
> throttling after only two unproductive memory passes. Four seemed quite
> arbitrary and only waiting for two passes allows us to complete the migration
> faster.
> 
> Signed-off-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
> Reviewed-by: Matthew Rosato <mjrosato@linux.vnet.ibm.com>
> ---
>  arch_init.c           | 95 +++++++++++++++++----------------------------------
>  migration/migration.c |  9 +++++
>  2 files changed, 41 insertions(+), 63 deletions(-)
> 

> +static void mig_throttle_guest_down(void)
> +{
> +    CPUState *cpu;
> +
> +    CPU_FOREACH(cpu) {
> +        /* We have not started throttling yet. Lets start it.*/

s/Lets/Let's/
s|it.*/|it. */|

> +        if (!cpu_throttle_active(cpu)) {
> +            cpu_throttle_start(cpu, 0.2);
> +        }
> +
> +        /* Throttling is already in place. Just increase the throttling rate */
> +        else {

Unusual layout.  More typical would be:

if (...) {
   ...
} else {
   /* comment */
   ...
}

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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