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| author | Ricardo Koller <ricarkol@google.com> | 2023-04-26 19:23:23 +0200 |
|---|---|---|
| committer | Oliver Upton <oliver.upton@linux.dev> | 2023-05-16 19:39:18 +0200 |
| commit | 2f440b72e852be428540579b5813ba2b8236578d (patch) | |
| tree | c4be44262abb5c8da28ca42115b6ae7e885693d4 /Documentation/virt | |
| parent | KVM: arm64: Export kvm_are_all_memslots_empty() (diff) | |
| download | linux-2f440b72e852be428540579b5813ba2b8236578d.tar.xz linux-2f440b72e852be428540579b5813ba2b8236578d.zip | |
KVM: arm64: Add KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE
Add a capability for userspace to specify the eager split chunk size.
The chunk size specifies how many pages to break at a time, using a
single allocation. Bigger the chunk size, more pages need to be
allocated ahead of time.
Suggested-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Ricardo Koller <ricarkol@google.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Link: https://lore.kernel.org/r/20230426172330.1439644-6-ricarkol@google.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Diffstat (limited to 'Documentation/virt')
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index add067793b90..656bd293c8f4 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -8445,6 +8445,33 @@ structure. When getting the Modified Change Topology Report value, the attr->addr must point to a byte where the value will be stored or retrieved from. +8.40 KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE +--------------------------------------- + +:Capability: KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE +:Architectures: arm64 +:Type: vm +:Parameters: arg[0] is the new split chunk size. +:Returns: 0 on success, -EINVAL if any memslot was already created. + +This capability sets the chunk size used in Eager Page Splitting. + +Eager Page Splitting improves the performance of dirty-logging (used +in live migrations) when guest memory is backed by huge-pages. It +avoids splitting huge-pages (into PAGE_SIZE pages) on fault, by doing +it eagerly when enabling dirty logging (with the +KVM_MEM_LOG_DIRTY_PAGES flag for a memory region), or when using +KVM_CLEAR_DIRTY_LOG. + +The chunk size specifies how many pages to break at a time, using a +single allocation for each chunk. Bigger the chunk size, more pages +need to be allocated ahead of time. + +The chunk size needs to be a valid block size. The list of acceptable +block sizes is exposed in KVM_CAP_ARM_SUPPORTED_BLOCK_SIZES as a +64-bit bitmap (each bit describing a block size). The default value is +0, to disable the eager page splitting. + 9. Known KVM API problems ========================= |