Re: [Qemu-devel] [PATCH v5 2/5] migration: Parameters for auto-converge cpu throttling

[Eric Blake <eblake@redhat.com>]

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On 09/01/2015 08:46 AM, Jason J. Herne wrote:
> Add migration parameters to allow the user to adjust the parameters
> that control cpu throttling when auto-converge is in effect. The added
> parameters are as follows:
> 
> x-cpu-throttle-initial : Initial percantage of time guest cpus are throttled
> when migration auto-converge is activated.
> 
> x-cpu-throttle-increment: throttle percantage increase each time
> auto-converge detects that migration is not making progress.

Marked experimental; do we think it will be promoted to stable before
2.5 is released?

What happens if I set throttle-initial to 50 and throttle-increment to
50?  The previous patch required throttle percentage to be between 1 and
99 inclusive; does that mean I cap out at 99 instead of an invalid
throttle of 100?

> 
> Signed-off-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  hmp.c                 | 16 ++++++++++++++++
>  migration/migration.c | 46 +++++++++++++++++++++++++++++++++++++++++++++-
>  qapi-schema.json      | 33 ++++++++++++++++++++++++++++++---
>  3 files changed, 91 insertions(+), 4 deletions(-)
> 

> +++ b/qapi-schema.json
> @@ -587,10 +587,18 @@
>  #          compression, so set the decompress-threads to the number about 1/4
>  #          of compress-threads is adequate.
>  #
> +# @x-cpu-throttle-initial: Initial percentage of time guest cpus are throttled
> +#                          when migration auto-converge is activated.
> +#                          (Since 2.4)
> +#
> +# @x-cpu-throttle-increment: throttle percentage increase each time
> +#                            auto-converge detects that migration is not making
> +#                            progress. (Since 2.4)

We've missed 2.4; these lines need to say (Since 2.5).

>  # Since: 2.4
>  ##
>  { 'enum': 'MigrationParameter',
> -  'data': ['compress-level', 'compress-threads', 'decompress-threads'] }
> +  'data': ['compress-level', 'compress-threads', 'decompress-threads',
> +           'x-cpu-throttle-initial', 'x-cpu-throttle-increment'] }
>  
>  #
>  # @migrate-set-parameters
> @@ -603,12 +611,22 @@
>  #
>  # @decompress-threads: decompression thread count
>  #
> +# @x-cpu-throttle-initial: Initial percentage of time guest cpus are throttled
> +#                          when migration auto-converge is activated.
> +#                          (Since 2.4)

Would be nice to document the default (20).

> +#
> +# @x-cpu-throttle-increment: throttle percentage increase each time
> +#                            auto-converge detects that migration is not making
> +#                            progress. (Since 2.4)

And again (10).  Also, same comment about needing 2.5.

> @@ -618,13 +636,22 @@
>  # @compress-threads: compression thread count
>  #
>  # @decompress-threads: decompression thread count
> +# @x-cpu-throttle-initial: Initial percentage of time guest cpus are throttled
> +#                          when migration auto-converge is activated.
> +#                          (Since 2.4)
> +#
> +# @x-cpu-throttle-increment: throttle percentage increase each time
> +#                            auto-converge detects that migration is not making
> +#                            progress. (Since 2.4)

2.5.

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


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