On Wed, Jan 31, 2024 at 06:31:10PM +0800, pet...@redhat.com wrote: > From: Peter Xu <pet...@redhat.com> > > This patch redefines the interfacing of ->send_prepare(). It further > simplifies multifd_send_thread() especially on zero copy. > > Now with the new interface, we require the hook to do all the work for > preparing the IOVs to send. After it's completed, the IOVs should be ready > to be dumped into the specific multifd QIOChannel later. > > So now the API looks like: > > p->pages -----------> send_prepare() -------------> IOVs > > This also prepares for the case where the input can be extended to even not > any p->pages. But that's for later. > > This patch will achieve similar goal of what Fabiano used to propose here: > > https://lore.kernel.org/r/20240126221943.26628-1-faro...@suse.de > > However the send() interface may not be necessary. I'm boldly attaching a > "Co-developed-by" for Fabiano. > > Co-developed-by: Fabiano Rosas <faro...@suse.de> > Signed-off-by: Peter Xu <pet...@redhat.com>
Just a heads-up: I plan to squash something like below also into it. That's mostly Fabiano's: https://lore.kernel.org/r/20240126221943.26628-6-faro...@suse.de But instead of overwritting write_flags in the hook, I made it a conditional "OR" just in case we'll extend write_flags later in common paths and get it overlooked. In short, I'll keep all zerocopy changes together in this single patch, hopefully clearer. ===== diff --git a/migration/multifd.c b/migration/multifd.c index cd4467aff4..6aa44340de 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -50,15 +50,15 @@ typedef struct { /** * nocomp_send_setup: setup send side * - * For no compression this function does nothing. - * - * Returns 0 for success or -1 for error - * * @p: Params for the channel that we are using * @errp: pointer to an error */ static int nocomp_send_setup(MultiFDSendParams *p, Error **errp) { + if (migrate_zero_copy_send()) { + p->write_flags |= QIO_CHANNEL_WRITE_FLAG_ZERO_COPY; + } + return 0; } -- Peter Xu
