[libvirt] [PATCH 3/4] qemu: managedsave: Add support for compressing managed save images

[Peter Krempa]

On 10/09/13 18:33, Daniel P. Berrange wrote:
> On Wed, Oct 09, 2013 at 06:31:31PM +0200, Peter Krempa wrote:
>> The regular save image code has the support to compress images using a
>> specified algorithm. This was not implemented for managed save although
>> it shares most of the backend code.
>> ---
>>  src/qemu/qemu.conf     |  6 ++++++
>>  src/qemu/qemu_conf.c   |  2 ++
>>  src/qemu/qemu_conf.h   |  1 +
>>  src/qemu/qemu_driver.c | 23 +++++++++++++++++++++--
>>  4 files changed, 30 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/qemu/qemu.conf b/src/qemu/qemu.conf
>> index 5fd6263..7cf67df 100644
>> --- a/src/qemu/qemu.conf
>> +++ b/src/qemu/qemu.conf
>> @@ -278,8 +278,14 @@
>>  # the requested compression program can't be found, this falls
>>  # back to "raw" compression.
>>  #
>> +# managedsave_image_format is used when a domain is saved to a location managed
>> +# by libvirt for example by using 'virsh managedsave'.  It is an error if the
>> +# specified format isn't valid, or the requested compression program can't be
>> +# found.
>> +#
>>  #save_image_format = "raw"
>>  #dump_image_format = "raw"
>> +#managedsave_image_format = "raw"
> 
> I'm wondering if we could justifiably just use the existing 'save_image_format'
> for managed save too.

Technically we definitely could. The formats are automatically detected.

> 
> dump needed a separate option since that's a clearly semantically different
> API set, but save vs managed save is basically just API sugar, so I feel
> we could just use the same config option.

I chose to do it in a configurable manner as the use of a compression
algorithm sometimes introduces significant slowing of the saving process
which might be unfortunate when managed save is used for saving guests
at host shutdown while use of the regular save mechanism can tolerate
longer saving periods.

Peter

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