From: "LIZHAOXIN1 [李照鑫]" <LIZHAOXIN1@kingsoft.com>
To: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"quintela@redhat.com" <quintela@redhat.com>,
"dgilbert@redhat.com" <dgilbert@redhat.com>
Cc: "LIZHAOXIN1 [李照鑫]" <LIZHAOXIN1@kingsoft.com>,
"sunhao2 [孙昊]" <sunhao2@kingsoft.com>,
"DENGLINWEN [邓林文]" <DENGLINWEN@kingsoft.com>,
"YANGFENG1 [杨峰]" <YANGFENG1@kingsoft.com>
Subject: Issue Report: When VM memory is extremely large, downtime for RDMA migration is high. (64G mem --> extra 400ms)
Date: Thu, 15 Apr 2021 01:54:19 +0000 [thread overview]
Message-ID: <0e83bff996fd4c098b679f04323d25e6@kingsoft.com> (raw)
Hi:
When I tested RDMA live migration, I found that the downtime increased as the VM's memory increased.
My Mellanox network card is [ConnectX-4 LX] and the driver is MLNX-5.2, My VM memory size is 64GB, downtime is 430ms when I migrate using the following parameters:
virsh migrate --live --p2p --persistent --copy-storage-inc --auto-converge --verbose --listen-address 0.0.0.0 --rdma-pin-all --migrateuri rdma://192.168.0.2 [VM] qemu+tcp://192.168.0.2/system
The extra time, about 400ms, which is how long it takes RDMA to deregister memory (the function: ibv_dereg_mr) after memory migration is complete, is before qmp_cont and therefore part of downtime.
How do we reduce this downtime? Like deregister memory somewhere else?
If anything wrong, Please point out.
Thanks!
reply other threads:[~2021-04-15 4:05 UTC|newest]
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