Re: [PATCH v5 07/23] migration/ram: Introduce 'mapped-ram' migration capability

[Peter Xu <peterx@redhat.com>]

On Wed, Feb 28, 2024 at 12:21:11PM -0300, Fabiano Rosas wrote:
> Add a new migration capability 'mapped-ram'.
> 
> The core of the feature is to ensure that RAM pages are mapped
> directly to offsets in the resulting migration file instead of being
> streamed at arbitrary points.
> 
> The reasons why we'd want such behavior are:
> 
>  - The resulting file will have a bounded size, since pages which are
>    dirtied multiple times will always go to a fixed location in the
>    file, rather than constantly being added to a sequential
>    stream. This eliminates cases where a VM with, say, 1G of RAM can
>    result in a migration file that's 10s of GBs, provided that the
>    workload constantly redirties memory.
> 
>  - It paves the way to implement O_DIRECT-enabled save/restore of the
>    migration stream as the pages are ensured to be written at aligned
>    offsets.
> 
>  - It allows the usage of multifd so we can write RAM pages to the
>    migration file in parallel.
> 
> For now, enabling the capability has no effect. The next couple of
> patches implement the core functionality.
> 
> Acked-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Fabiano Rosas <farosas@suse.de>

Reviewed-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu