Re: How to reduce IOWAIT and CPU idle time?

Hello Venkata,

Thank you for the reply!

I forgot to specify the application name.It is ZABBIX tool using postgreSQL
database. All types of queries are running slow and i can see application
is writing continuously.
Yesterday , i updated effective_io_concurrency to 25 which earlier set as
default. But this has not helped me to solve the problem.

Yes, you are right, the database size has grown from 5 GB database to 100
GB database and may be there is problem in slownesss in disk. However we
cannot replace the disk right now.

I ran vacuum and analyze manually on all the tables as well. Still it is
not helping. Can you think of any other setting which i should enable?

Thanks,
Samir Magar

On Sun, Sep 11, 2016 at 6:04 AM, Venkata B Nagothi <nag1010(at)gmail(dot)com>
wrote:

>
> On Sat, Sep 10, 2016 at 8:49 PM, Samir Magar <samirmagar8(at)gmail(dot)com>
> wrote:
>
>> Hello,
>>
>>
>> My Application has normally 25 to 30 connections and it is doing lot of
>> insert/update/delete operation.
>> The database size is 100GB.
>> iowait is at 40% to 45 % and CPU idle time is at 45% to 50%
>> TOTAL RAM = 8 GB TOTAL CPU = 4
>>
>> postgresql.conf parametre:
>>
>> shared_buffers = 2GB
>> work_mem = 100MB
>> effective_cache_size = 2GB
>> maintenance_work_mem = 500MB
>> autovacuum = off
>> wal_buffers = 64MB
>>
>>
>> How can i reduce iowait and CPU idle time. It is slowing all the queries.
>> The queries that used to take 1 sec,it is taking 12-15 seconds.
>>
>
> That does not point out the specific problem you are facing. Queries can
> slow down for a lot of reasons like as follows -
>
> - Lack of maintenance
> - Bloats in Tables and Indexes
> - Data size growth
> - If writes are slowing down, then it could be because of slow disks
>
> Are you saying that queries are slowing down when there are heavy writes ?
> Are you referring to SELECTs or all types of queries ?
>
> Regards,
> Venkata B N
>
> Fujitsu Australia
>