[Libguestfs] [PATCH v2v] v2v/v2v.ml: Choose nbdcopy max requests for implicit buffer of 64M

Pick the nbdcopy --requests parameter to target an implicit buffer size of 64M inside nbdcopy. However don't set nbdcopy --request < 64. If request_size == 256K (the default) => requests = 256 If request_size == 8M => requests = 64 (buffer size 512M) --- v2v/v2v.ml | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/v2v/v2v.ml b/v2v/v2v.ml index cadf864d5c..7bd47c1e7e 100644 --- a/v2v/v2v.ml +++ b/v2v/v2v.ml @@ -641,14 +641,27 @@ and nbdcopy ?request_size output_alloc input_uri output_uri = *) let cmd = ref [] in List.push_back_list cmd [ "nbdcopy"; input_uri; output_uri ]; + (match request_size with | None -> () | Some size -> List.push_back cmd (sprintf "--request-size=%d" size) ); + (* Choose max requests to target an implicit buffer size of 64M. *) + let requests = + let target_buffer_size = 64 * 1024 * 1024 in + let request_size = + match request_size with + | None -> 256 * 1024 (* default in nbdcopy 1.10+ *) + | Some size -> size in + min 64 (target_buffer_size / request_size) in + List.push_back cmd (sprintf "--requests=%d" requests); + List.push_back cmd "--flush"; (*List.push_back cmd "--verbose";*) + if not (quiet ()) then List.push_back cmd "--progress"; if output_alloc = Types.Preallocated then List.push_back cmd "--allocated"; + let cmd = !cmd in if run_command cmd <> 0 then -- 2.35.1