Re: [9.4 bug] The database server hangs with write-heavy workload on Windows

On 10/10/2014 05:08 PM, MauMau wrote:
> From: "Craig Ringer" <craig(at)2ndquadrant(dot)com>
>> It sounds like they've produced a test case, so they should be able to
>> with a bit of luck.
>>
>> Or even better, send you the test case.
>
> I asked the user about this. It sounds like the relevant test case consists
> of many scripts. He explained to me that the simplified test steps are:
>
> 1. initdb
> 2. pg_ctl start
> 3. Create 16 tables. Each of those tables consist of around 10 columns.
> 4. Insert 1000 rows into each of those 16 tables.
> 5. Launch 16 psql sessions concurrently. Each session updates all 1000 rows
> of one table, e.g., session 1 updates table 1, session 2 updates table 2,
> and so on.
> 6. Repeat step 5 50 times.
>
> This sounds a bit complicated, but I understood that the core part is 16
> concurrent updates, which should lead to contention on xlog insert slots
> and/or spinlocks.

I was able to reproduce this. I reduced wal_buffers to 64kB, and
NUM_XLOGINSERT_LOCKS to 4 to increase the probability of the deadlock,
and ran a test case as above on my laptop for several hours, and it
finally hung. Will investigate...

- Heikki