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migration/multifd: cache channel count in multifd_send_sync_main

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multifd_send_sync_main() is called once per RAM synchronization round
during live migration.  It iterates over all multifd channels twice
(signal loop + wait loop), calling migrate_multifd_channels()
independently in each loop header.

Cache migrate_multifd_channels() in a local thread_count variable at
function entry, matching the pattern already used in
multifd_send_setup() and multifd_recv_setup().  This eliminates 2
redundant config lookups per sync call.

Signed-off-by: Bin Guo <guobin@linux.alibaba.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20260518110112.21395-9-guobin@linux.alibaba.com
Signed-off-by: Peter Xu <peterx@redhat.com>
This commit is contained in:
Bin Guo
2026-05-18 19:01:12 +08:00
committed by Peter Xu
parent 75d782a1e9
commit ba92642400
1 changed files with 4 additions and 2 deletions
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6
migration/multifd.c
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@@ -611,13 +611,15 @@ static int multifd_zero_copy_flush(QIOChannel *c)
int multifd_send_sync_main(MultiFDSyncReq req)
{
int i;
int thread_count;
bool flush_zero_copy;
assert(req != MULTIFD_SYNC_NONE);
thread_count = migrate_multifd_channels();
flush_zero_copy = migrate_zero_copy_send();
for (i = 0; i < migrate_multifd_channels(); i++) {
for (i = 0; i < thread_count; i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
if (multifd_send_should_exit()) {
@@ -634,7 +636,7 @@ int multifd_send_sync_main(MultiFDSyncReq req)
qatomic_set(&p->pending_sync, req);
qemu_sem_post(&p->sem);
}
for (i = 0; i < migrate_multifd_channels(); i++) {
for (i = 0; i < thread_count; i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
if (multifd_send_should_exit()) {