Subject: Re: [Firebird-devel] [FB-Tracker] Created:
(CORE-5419) Index garbage collection on varchar
column causes server to hang



11.01.2017 16:01, Alex Peshkoff wrote:
> On 01/11/17 16:19, Vlad Khorsun wrote:
>> 11.01.2017 15:09, Alex Peshkoff wrote:
>>>
>>>>> Could you try fb2.5 (as i did) ?
>>>> Will do.
>>>>
>>> On 2.5 I see approx 50% slowdown when GC is in progress. Same slowdown
>>> is present when 'delete from test' is executed.
>> Slowdown of what operation ?
>>
>>> Nothing special for GC, but must say that master seems to miss even this
>>> slowdown.
>> Master is out of question ;)
>>
>>> Rather hard to say for sure cause execution time of test
>>> connection varies from 0.01 sec to 0.02 sec for 2.5, not more. For
>>> master it seems to be almost always 0.01.
>> What is done in that test connection ? Could you try to create table
>> and insert record into it ?
>
> Run th following test:
> for i in `seq 10000`; do echo IIIIIIII $i; time (echo 'create table tt(x
> int); commit; insert into tt values(1); commit; drop table tt;'|./isql
> todel.fdb) ; sleep 1; done
>
> No activity - 0.8 - 0.9 sec
> delete from test - 1.4 - 2.5 sec
> select (with GC) - 1.9 - 3.8 sec
>
> I.e. slowdown is obviously present but it's too far from being irresponsive.

Thanks. Sad you can't reproduce it. I do it easily. AST thread is blocked at
Database::Sync::lock on syncMutex.enter() despite of a lot of checkouts in
worker
thread. Interesting is that debugger intrusion (just a breakpoint on
THREAD_YIELD()
at JRD_reschedule()) often helps AST thread to got control and unblock...

Regards,
Vlad
r>

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