Ivan Ren <reny...@gmail.com> wrote: > From: Ivan Ren <ivan...@tencent.com> > > This patch fix a multifd migration bug in migration speed calculation, this > problem can be reproduced as follows: > 1. start a vm and give a heavy memory write stress to prevent the vm be > successfully migrated to destination > 2. begin a migration with multifd > 3. migrate for a long time [actually, this can be measured by transferred > bytes] > 4. migrate cancel > 5. begin a new migration with multifd, the migration will directly run into > migration_completion phase > > Reason as follows: > > Migration update bandwidth and s->threshold_size in function > migration_update_counters after BUFFER_DELAY time: > > current_bytes = migration_total_bytes(s); > transferred = current_bytes - s->iteration_initial_bytes; > time_spent = current_time - s->iteration_start_time; > bandwidth = (double)transferred / time_spent; > s->threshold_size = bandwidth * s->parameters.downtime_limit; > > In multifd migration, migration_total_bytes function return > qemu_ftell(s->to_dst_file) + ram_counters.multifd_bytes. > s->iteration_initial_bytes will be initialized to 0 at every new migration, > but ram_counters is a global variable, and history migration data will be > accumulated. So if the ram_counters.multifd_bytes is big enough, it may lead > pending_size >= s->threshold_size become false in migration_iteration_run > after the first migration_update_counters. > > Signed-off-by: Ivan Ren <ivan...@tencent.com>
Reviewed-by: Juan Quintela <quint...@redhat.com>
