Re: [Qemu-devel] [PATCH 5/5] disk_deadlines: add info disk-deadlines option

[Eric Blake]

On 09/08/2015 02:00 AM, Denis V. Lunev wrote:
> From: Raushaniya Maksudova <address@hidden>
> 
> This patch adds "info disk-deadlines" qemu-monitor option that prints
> dump of all disk requests which caused a disk deadline in Guest OS
> from the very start of Virtual Machine:
> 
>    disk_id  type       size total_time        start_time
> .--------------------------------------------------------
>   ide0-hd1 FLUSH         0b 46.403s     22232930059574ns
>   ide0-hd1 FLUSH         0b 57.591s     22451499241285ns
>   ide0-hd1 FLUSH         0b 103.482s    22574100547397ns
> 
> Signed-off-by: Raushaniya Maksudova <address@hidden>
> Signed-off-by: Denis V. Lunev <address@hidden>
> CC: Stefan Hajnoczi <address@hidden>
> CC: Kevin Wolf <address@hidden>
> CC: Markus Armbruster <address@hidden>
> CC: Luiz Capitulino <address@hidden>
> ---

qapi interface review only:


> +++ b/qapi-schema.json
> @@ -3808,3 +3808,36 @@
>  
>  # Rocker ethernet network switch
>  { 'include': 'qapi/rocker.json' }
> +
> +## @DiskDeadlinesInfo
> +#
> +# Contains info about late requests which caused VM stopping
> +#
> +# @disk-id: name of disk (unique for each disk)

Mark this with '#optional', and maybe describe why it would be missing.
 Does this correspond to the BDS node name where the deadline expired,
in which case 'node' might be a nicer name than 'disk-id'?

> +#
> +# @type: type of request could be READ, WRITE or FLUSH

Likewise for using #optional. Please make this an enum type, not an
open-coded string.

> +#
> +# @size: size in bytes

of the failed request? Should you also mention which offset the failed
request started at?

> +#
> +# @total-time-ns: total time of request execution
> +#
> +# @start-time-ns: indicates the start of request execution
> +#
> +# Since: 2.5
> +##
> +{ 'struct': 'DiskDeadlinesInfo',
> +  'data'  : { '*disk-id': 'str',
> +              '*type': 'str',
> +              'size': 'uint64',
> +              'total-time-ns': 'uint64',
> +              'start-time-ns': 'uint64' } }
> +##
> +# @query-disk-deadlines:
> +#
> +# Returns information about last late disk requests.
> +#
> +# Returns: a list of @DiskDeadlinesInfo
> +#
> +# Since: 2.5
> +##
> +{ 'command': 'query-disk-deadlines', 'returns': ['DiskDeadlinesInfo'] }

Should it be possible to filter to deadlines missed for a specific node,
by having an arguments with an optional node name?

Should any of the existing query-block or similar commands be modified
to make it obvious that there are missed deadline stats, and that it
would be useful to call query-disk-deadlines to learn more about them?

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

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