On 10/10/24 15:29, Daniel P. Berrangé wrote:
> On Thu, Aug 08, 2024 at 05:38:10PM -0600, Jim Fehlig via Devel wrote:
>> From: Claudio Fontana <cfontana@xxxxxxx>
>>
>> Add a new VIR_DOMAIN_SAVE_PARALLEL flag to the save and restore
>> APIs, which can be used to specify the use of multiple, parallel
>> channels for saving a domain. The number of parallel channels
>> can be set using the VIR_DOMAIN_SAVE_PARAM_PARALLEL_CONNECTIONS
>> typed parameter.
>>
>> Signed-off-by: Claudio Fontana <cfontana@xxxxxxx>
>> Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx>
>> ---
>> include/libvirt/libvirt-domain.h | 13 +++++++++++++
>> src/libvirt-domain.c | 6 ++++++
>> 2 files changed, 19 insertions(+)
>>
>> diff --git a/include/libvirt/libvirt-domain.h b/include/libvirt/libvirt-domain.h
>> index 4266237abe..f4bf9c3cdb 100644
>> --- a/include/libvirt/libvirt-domain.h
>> +++ b/include/libvirt/libvirt-domain.h
>> @@ -1596,6 +1596,7 @@ typedef enum {
>> VIR_DOMAIN_SAVE_RUNNING = 1 << 1, /* Favor running over paused (Since: 0.9.5) */
>> VIR_DOMAIN_SAVE_PAUSED = 1 << 2, /* Favor paused over running (Since: 0.9.5) */
>> VIR_DOMAIN_SAVE_RESET_NVRAM = 1 << 3, /* Re-initialize NVRAM from template (Since: 8.1.0) */
>> + VIR_DOMAIN_SAVE_PARALLEL = 1 << 4, /* Save and restore using parallel channels (Since: 10.6.0) */
>> } virDomainSaveRestoreFlags;
>>
>> int virDomainSave (virDomainPtr domain,
>> @@ -1641,6 +1642,18 @@ int virDomainRestoreParams (virConnectPtr conn,
>> */
>> # define VIR_DOMAIN_SAVE_PARAM_DXML "dxml"
>>
>> +/**
>> + * VIR_DOMAIN_SAVE_PARAM_PARALLEL_CONNECTIONS:
>> + *
>> + * this optional parameter mirrors the migration parameter
>> + * VIR_MIGRATE_PARAM_PARALLEL_CONNECTIONS.
>> + *
>> + * It specifies the number of extra connections to use when transfering state.
>> + *
>> + * Since: 10.6.0
>> + */
>> +# define VIR_DOMAIN_SAVE_PARAM_PARALLEL_CONNECTIONS "parallel.connections"
>
> "CONNECTIONS" is perhaps the wrong name, as that's kinda an impl
I would suggest CONNECTIONS it is the correct name.
> detail. How about VIR_MIGRATE_PARAM_PARALLEL_CPUS to reflect
> the number of CPUs we're going to burn time on.
This is another aspect of it, but I would suggest that _this_ is much more an implementation detail (inside qemu) on how the parallel connection is actually managed.
Maybe in the future there will be a pool of cpus serving this, or another optional way to serve the connections.
Considering the fact that libvirt _already has_ for regular migrations
{.typedParam = VIR_MIGRATE_PARAM_PARALLEL_CONNECTIONS,
.param = QEMU_MIGRATION_PARAM_MULTIFD_CHANNELS,
.party = QEMU_MIGRATION_SOURCE | QEMU_MIGRATION_DESTINATION},
which controls exactly the same QEMU parameter (ie the multifd-channels),
using anything else than --parallel-connections is in my opinion very surprising for the users (which would know what to expect from the same command line option),
and honestly simply absurd.
Thanks,
Claudio
>
>> +
>> /* See below for virDomainSaveImageXMLFlags */
>> char * virDomainSaveImageGetXMLDesc (virConnectPtr conn,
>> const char *file,
>> diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
>> index 5aedae1b49..32508a4ede 100644
>> --- a/src/libvirt-domain.c
>> +++ b/src/libvirt-domain.c
>> @@ -1010,6 +1010,9 @@ virDomainSaveFlags(virDomainPtr domain, const char *to,
>> * If VIR_DOMAIN_SAVE_PARAM_FILE is not provided then a managed save is
>> * performed (see virDomainManagedSave).
>> *
>> + * See VIR_DOMAIN_SAVE_PARAM_* for detailed description of accepted save
>> + * parameters.
>> + *
>> * Returns 0 in case of success and -1 in case of failure.
>> *
>> * Since: 8.4.0
>> @@ -1222,6 +1225,9 @@ virDomainRestoreFlags(virConnectPtr conn, const char *from, const char *dxml,
>> * now, VIR_DOMAIN_SAVE_PARAM_FILE is required but this requirement may
>> * be lifted in the future.
>> *
>> + * See VIR_DOMAIN_SAVE_PARAM_* for detailed description of accepted
>> + * restore parameters.
>> + *
>> * Returns 0 in case of success and -1 in case of failure.
>> *
>> * Since: 8.4.0
>> --
>> 2.35.3
>>
>
> With regards,
> Daniel
