migration/multifd: multifd_send_prepare_header()

Introduce a helper multifd_send_prepare_header() to setup the header packet
for multifd sender.

It's fine to setup the IOV[0] _before_ send_prepare() because the packet
buffer is already ready, even if the content is to be filled in.

With this helper, we can already slightly clean up the zero copy path.

Note that I explicitly put it into multifd.h, because I want it inlined
directly into multifd*.c where necessary later.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240202102857.110210-13-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
This commit is contained in:
Peter Xu 2024-02-02 18:28:46 +08:00
parent 8a9ef17380
commit 452b205702
2 changed files with 16 additions and 8 deletions

View file

@ -712,10 +712,14 @@ static void *multifd_send_thread(void *opaque)
if (qatomic_read(&p->pending_job)) {
MultiFDPages_t *pages = p->pages;
if (use_zero_copy_send) {
p->iovs_num = 0;
} else {
p->iovs_num = 1;
p->iovs_num = 0;
if (!use_zero_copy_send) {
/*
* Only !zerocopy needs the header in IOV; zerocopy will
* send it separately.
*/
multifd_send_prepare_header(p);
}
assert(pages->num);
@ -735,10 +739,6 @@ static void *multifd_send_thread(void *opaque)
if (ret != 0) {
break;
}
} else {
/* Send header using the same writev call */
p->iov[0].iov_len = p->packet_len;
p->iov[0].iov_base = p->packet;
}
ret = qio_channel_writev_full_all(p->c, p->iov, p->iovs_num, NULL,

View file

@ -209,5 +209,13 @@ typedef struct {
void multifd_register_ops(int method, MultiFDMethods *ops);
static inline void multifd_send_prepare_header(MultiFDSendParams *p)
{
p->iov[0].iov_len = p->packet_len;
p->iov[0].iov_base = p->packet;
p->iovs_num++;
}
#endif