Re: [Qemu-devel] [PATCH v4 0/3] High downtime with 95+ throttle pct

[Yury Kotov]

Ping ping

07.08.2019, 10:42, "Yury Kotov" <address@hidden>:
> Ping
>
> 23.07.2019, 16:42, "Yury Kotov" <address@hidden>:
>>  Hi,
>>
>>  V4:
>>  * The test was simplified to prevent false fails.
>>
>>  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 | 103 ++++++++++++++++++++++++++++++++++-----
>>   util/qemu-thread-posix.c | 40 ++++++++++-----
>>   util/qemu-thread-win32.c | 16 ++++++
>>   util/qsp.c | 18 +++++++
>>   6 files changed, 191 insertions(+), 31 deletions(-)
>>
>>  --
>>  2.22.0