Re: [PATCH 0/2] Increase amount of data for monitor to read

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

09.11.2020 11:50, Vladimir Sementsov-Ogievskiy wrote:
> 06.11.2020 15:42, Andrey Shinkevich wrote:
>> The subject was discussed here:
>> https://lists.gnu.org/archive/html/qemu-devel/2017-05/msg00206.html
>>
>> This series is a solution for the issue with QMP monitor buffered input.
>> A little parser is introduced to throttle JSON commands read from the
>> buffer so that QMP requests do not overwhelm the monitor input queue.
>> A side effect raised in the test #247 was managed in the first patch.
>> It may be considered as a workaround. Any sane fix suggested will be
>> appreciated.
>>
>> Note:
>> This series goes after the Vladimir's one:
>> '[PATCH v3 00/25] backup performance: block_status + async"'
>> To make the test #129 passed, the following patch should be applied first:
>> '[PATCH v3 01/25] iotests: 129 don't check backup "busy"'.
>>
> 
> Hi!
> 
> I tried the following test:
> 
> start qemu:
> 
>    ./qemu-system-x86_64 -qmp stdio
> 
> type the following in one line:
> 
>    { 'execute': 'qmp_capabilities' }{ 'execute': 'quit' }
> 
> press Enter.
> 
> Without your patches, the qemu quits immediately, printing double "{"return": {}}".
> With your patches applied qemu prints "{"return": {}}" only once and doesn't quit, until I press Enter the second time.


Positive thing: the patches do increase performance:

for me, the following command:

(echo "{ 'execute': 'qmp_capabilities' }"; for i in {1..10000}; do echo "{ 'execute': 'query-block-jobs' }"; done; echo "{ 'execute': 'quit' }" ) | time ./qemu-system-x86_64 -qmp stdio > /dev/null

shows 2.4s on master and 0.6s after patches


> 
> 
>> Andrey Shinkevich (2):
>>    iotests: add another bash sleep command to 247
>>    monitor: increase amount of data for monitor to read
>>
>>   chardev/char-fd.c          | 64 +++++++++++++++++++++++++++++++++++++++++++++-
>>   chardev/char-socket.c      | 54 +++++++++++++++++++++++++++-----------
>>   chardev/char.c             | 40 +++++++++++++++++++++++++++++
>>   include/chardev/char.h     | 15 +++++++++++
>>   monitor/monitor.c          |  2 +-
>>   tests/qemu-iotests/247     |  2 ++
>>   tests/qemu-iotests/247.out |  1 +
>>   7 files changed, 161 insertions(+), 17 deletions(-)
>>
> 
> 


-- 
Best regards,
Vladimir