Re: New statistics for tuning WAL buffer size

On 2020/08/19 14:10, Masahiro Ikeda wrote:
> On 2020-08-19 13:49, tsunakawa.takay@fujitsu.com wrote:
>> From: Masahiro Ikeda <ikedamsh@oss.nttdata.com>
>>> If my understanding is correct, we have to measure the performance
>>> impact first.
>>> Do you know HariBabu is now trying to solve it? If not, I will try to
>>> modify patches to apply HEAD.
>>
>> No, he's not doing it anymore.  It'd be great if you could resume it.
> 
> OK, thanks.
> 
>> However, I recommend sharing your understanding about what were the
>> issues with those two threads and how you're trying to solve them.
>> Was the performance overhead the blocker in both of the threads?
> 
> In my understanding, some comments are not solved in both of the threads.
> I think the following works are remained.
> 
> 1) Modify patches to apply HEAD
> 2) Get consensus what metrics we collect and how to use them for tuning.

I agree to expose the number of WAL write caused by full of WAL buffers.
It's helpful when tuning wal_buffers size. Haribabu separated that number
into two fields in his patch; one is the number of WAL write by backend,
and another is by background processes and workers. But I'm not sure
how useful such separation is. I'm ok with just one field for that number.

Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION