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[Qemu-devel] [PATCH v3 0/3] High downtime with 95+ throttle pct
From: |
Yury Kotov |
Subject: |
[Qemu-devel] [PATCH v3 0/3] High downtime with 95+ throttle pct |
Date: |
Thu, 18 Jul 2019 12:17:23 +0300 |
Hi,
V3:
* Rebase fixes (migrate_set_parameter -> migrate_set_parameter_int)
V2:
* Added a test
* Fixed qemu_cond_timedwait for qsp
I wrote a test for migration auto converge and found out a strange thing:
1. Enable auto converge
2. Set max-bandwidth 1Gb/s
3. Set downtime-limit 1ms
4. Run standard test (just writes a byte per page)
5. Wait for converge
6. It's converged with 99% throttle percentage
7. The result downtime was about 300-600ms <<<<
It's much higher than expected 1ms. I figured out that cpu_throttle_thread()
function sleeps for 100ms+ for high throttle percentage (>=95%) in VCPU thread.
And it sleeps even after a cpu kick.
Fixed it by using timedwait for ms part of sleep.
E.g timedwait(halt_cond, 1ms) + usleep(500).
Regards,
Yury
Yury Kotov (3):
qemu-thread: Add qemu_cond_timedwait
cpus: Fix throttling during vm_stop
tests/migration: Add a test for auto converge
cpus.c | 27 ++++++---
include/qemu/thread.h | 18 ++++++
tests/migration-test.c | 119 +++++++++++++++++++++++++++++++++++----
util/qemu-thread-posix.c | 40 +++++++++----
util/qemu-thread-win32.c | 16 ++++++
util/qsp.c | 18 ++++++
6 files changed, 207 insertions(+), 31 deletions(-)
--
2.22.0