Re: Very poor read performance, query independent

On Wed, Jul 12, 2017 at 9:38 AM, Charles Nadeau <charles(dot)nadeau(at)gmail(dot)com>
wrote:

> Rick,
>
> Should the number of page should always be correlated to the VmPeak of the
> postmaster or could it be set to reflect shared_buffer or another setting?
> Thanks!
>
>
The documentation implies that you may need to adjust its size when you
change shared_buffer settings.

I usually check it every now and then (I haven't build a formal monitor
yet.) to see if all of the huge pages are free/used and if it looks like
they are all getting consumed - consider bumping it higher. If there are
lots free, you are probably fine.

cat /proc/meminfo | grep -i "^huge"

--

Also regarding my note on effective_io_concurrency, which I'm not sure you
tried tweaking yet.

With file system and hardware caching between you and your spindles, your
best setting for effective_io_concurrency may be much higher than the
actual number of spindles. It is worth experimenting with. If you can,
try several values. You can use pg_bench to put consistent workloads on
your database for measurement purposes.

Charles
>
> On Mon, Jul 10, 2017 at 5:25 PM, Rick Otten <rottenwindfish(at)gmail(dot)com>
> wrote:
>
>> Although probably not the root cause, at the least I would set up
>> hugepages ( https://www.postgresql.org/docs/9.6/static/kernel-resourc
>> es.html#LINUX-HUGE-PAGES ), and bump effective_io_concurrency up quite a
>> bit as well (256 ?).
>>
>>