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migration/multifd: Support outgoing fixed-ram stream format

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The new fixed-ram stream format uses a file transport and puts ram
pages in the migration file at their respective offsets and can be
done in parallel by using the pwritev system call which takes iovecs
and an offset.

Add support to enabling the new format along with multifd to make use
of the threading and page handling already in place.

This requires multifd to stop sending headers and leaving the stream
format to the fixed-ram code. When it comes time to write the data, we
need to call a version of qio_channel_write that can take an offset.

Usage on HMP is:

(qemu) stop
(qemu) migrate_set_capability multifd on
(qemu) migrate_set_capability fixed-ram on
(qemu) migrate_set_parameter max-bandwidth 0
(qemu) migrate_set_parameter multifd-channels 8
(qemu) migrate file:migfile

Signed-off-by: Fabiano Rosas <farosas@suse.de>
This commit is contained in:
Fabiano Rosas
2023-03-21 11:17:11 -03:00
parent b0a05de4bd
commit a110fcb9fb
2 changed files with 41 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

43
migration/multifd.c
View File

@@ -260,6 +260,19 @@ static void multifd_pages_clear(MultiFDPages_t *pages)
g_free(pages);
}
static void multifd_set_file_bitmap(MultiFDSendParams *p)
{
MultiFDPages_t *pages = p->pages;
if (!pages->block) {
return;
}
for (int i = 0; i < p->normal_num; i++) {
ramblock_set_shadow_bmap_atomic(pages->block, pages->offset[i]);
}
}
static void multifd_send_fill_packet(MultiFDSendParams *p)
{
MultiFDPacket_t *packet = p->packet;
@@ -606,6 +619,10 @@ int multifd_send_sync_main(QEMUFile *f)
}
}
if (!migrate_multifd_packets()) {
return 0;
}
/*
* When using zero-copy, it's necessary to flush the pages before any of
* the pages can be sent again, so we'll make sure the new version of the
@@ -689,6 +706,8 @@ static void *multifd_send_thread(void *opaque)
if (p->pending_job) {
uint32_t flags;
uint64_t write_base;
p->normal_num = 0;
if (!use_packets || use_zero_copy_send) {
@@ -713,6 +732,16 @@ static void *multifd_send_thread(void *opaque)
if (use_packets) {
multifd_send_fill_packet(p);
p->num_packets++;
write_base = 0;
} else {
multifd_set_file_bitmap(p);
/*
* If we subtract the host page now, we don't need to
* pass it into qio_channel_write_full_all() below.
*/
write_base = p->pages->block->pages_offset -
(uint64_t)p->pages->block->host;
}
flags = p->flags;
@@ -740,8 +769,9 @@ static void *multifd_send_thread(void *opaque)
p->iov[0].iov_base = p->packet;
}
ret = qio_channel_writev_full_all(p->c, p->iov, p->iovs_num, NULL,
0, p->write_flags, &local_err);
ret = qio_channel_write_full_all(p->c, p->iov, p->iovs_num,
write_base, NULL, 0,
p->write_flags, &local_err);
if (ret != 0) {
break;
}
@@ -758,6 +788,13 @@ static void *multifd_send_thread(void *opaque)
} else if (p->quit) {
qemu_mutex_unlock(&p->mutex);
break;
} else if (!use_packets) {
/*
* When migrating to a file there's not need for a SYNC
* packet, the channels are ready right away.
*/
qemu_sem_post(&multifd_send_state->channels_ready);
qemu_mutex_unlock(&p->mutex);
} else {
qemu_mutex_unlock(&p->mutex);
/* sometimes there are spurious wakeups */
@@ -981,6 +1018,8 @@ int multifd_save_setup(Error **errp)
if (migrate_zero_copy_send()) {
p->write_flags = QIO_CHANNEL_WRITE_FLAG_ZERO_COPY;
} else if (!use_packets) {
p->write_flags |= QIO_CHANNEL_WRITE_FLAG_WITH_OFFSET;
} else {
p->write_flags = 0;
}

6
migration/options.c
View File

@@ -594,12 +594,6 @@ bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp)
}
if (new_caps[MIGRATION_CAPABILITY_FIXED_RAM]) {
if (new_caps[MIGRATION_CAPABILITY_MULTIFD]) {
error_setg(errp,
"Fixed-ram migration is incompatible with multifd");
return false;
}
if (new_caps[MIGRATION_CAPABILITY_XBZRLE]) {
error_setg(errp,
"Fixed-ram migration is incompatible with xbzrle");