103 lines
4.0 KiB
Diff
103 lines
4.0 KiB
Diff
From 33a38fef5e889b45571228bde519746fd90d8877 Mon Sep 17 00:00:00 2001
|
|
From: Leonardo Bras <leobras@redhat.com>
|
|
Date: Wed, 18 May 2022 02:52:25 -0300
|
|
Subject: [PATCH 22/37] multifd: Send header packet without flags if
|
|
zero-copy-send is enabled
|
|
MIME-Version: 1.0
|
|
Content-Type: text/plain; charset=UTF-8
|
|
Content-Transfer-Encoding: 8bit
|
|
|
|
RH-Author: Leonardo Brás <leobras@redhat.com>
|
|
RH-MergeRequest: 191: MSG_ZEROCOPY + Multifd @ rhel8.7
|
|
RH-Commit: [22/26] 9abfee42b72f11911cf128519826d09cbd2f5bc3
|
|
RH-Bugzilla: 2072049
|
|
RH-Acked-by: Peter Xu <peterx@redhat.com>
|
|
RH-Acked-by: Daniel P. Berrangé <berrange@redhat.com>
|
|
RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
|
|
|
|
Since d48c3a0445 ("multifd: Use a single writev on the send side"),
|
|
sending the header packet and the memory pages happens in the same
|
|
writev, which can potentially make the migration faster.
|
|
|
|
Using channel-socket as example, this works well with the default copying
|
|
mechanism of sendmsg(), but with zero-copy-send=true, it will cause
|
|
the migration to often break.
|
|
|
|
This happens because the header packet buffer gets reused quite often,
|
|
and there is a high chance that by the time the MSG_ZEROCOPY mechanism get
|
|
to send the buffer, it has already changed, sending the wrong data and
|
|
causing the migration to abort.
|
|
|
|
It means that, as it is, the buffer for the header packet is not suitable
|
|
for sending with MSG_ZEROCOPY.
|
|
|
|
In order to enable zero copy for multifd, send the header packet on an
|
|
individual write(), without any flags, and the remanining pages with a
|
|
writev(), as it was happening before. This only changes how a migration
|
|
with zero-copy-send=true works, not changing any current behavior for
|
|
migrations with zero-copy-send=false.
|
|
|
|
Signed-off-by: Leonardo Bras <leobras@redhat.com>
|
|
Reviewed-by: Peter Xu <peterx@redhat.com>
|
|
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
|
|
Message-Id: <20220513062836.965425-8-leobras@redhat.com>
|
|
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
|
|
(cherry picked from commit b7dbdd8e76cd03453c234dbb9578d20969859d74)
|
|
Signed-off-by: Leonardo Bras <leobras@redhat.com>
|
|
---
|
|
migration/multifd.c | 22 +++++++++++++++++++---
|
|
1 file changed, 19 insertions(+), 3 deletions(-)
|
|
|
|
diff --git a/migration/multifd.c b/migration/multifd.c
|
|
index 1e34e01ebc..193f70cdba 100644
|
|
--- a/migration/multifd.c
|
|
+++ b/migration/multifd.c
|
|
@@ -624,6 +624,7 @@ static void *multifd_send_thread(void *opaque)
|
|
MultiFDSendParams *p = opaque;
|
|
Error *local_err = NULL;
|
|
int ret = 0;
|
|
+ bool use_zero_copy_send = migrate_use_zero_copy_send();
|
|
|
|
trace_multifd_send_thread_start(p->id);
|
|
rcu_register_thread();
|
|
@@ -646,9 +647,14 @@ static void *multifd_send_thread(void *opaque)
|
|
if (p->pending_job) {
|
|
uint64_t packet_num = p->packet_num;
|
|
uint32_t flags = p->flags;
|
|
- p->iovs_num = 1;
|
|
p->normal_num = 0;
|
|
|
|
+ if (use_zero_copy_send) {
|
|
+ p->iovs_num = 0;
|
|
+ } else {
|
|
+ p->iovs_num = 1;
|
|
+ }
|
|
+
|
|
for (int i = 0; i < p->pages->num; i++) {
|
|
p->normal[p->normal_num] = p->pages->offset[i];
|
|
p->normal_num++;
|
|
@@ -672,8 +678,18 @@ static void *multifd_send_thread(void *opaque)
|
|
trace_multifd_send(p->id, packet_num, p->normal_num, flags,
|
|
p->next_packet_size);
|
|
|
|
- p->iov[0].iov_len = p->packet_len;
|
|
- p->iov[0].iov_base = p->packet;
|
|
+ if (use_zero_copy_send) {
|
|
+ /* Send header first, without zerocopy */
|
|
+ ret = qio_channel_write_all(p->c, (void *)p->packet,
|
|
+ p->packet_len, &local_err);
|
|
+ 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_all(p->c, p->iov, p->iovs_num,
|
|
&local_err);
|
|
--
|
|
2.35.3
|
|
|