Re: Priority table or Cache table

On Tue, Aug 11, 2015 at 4:43 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Tue, Aug 11, 2015 at 11:31 AM, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>
> wrote:
>>
>> On Mon, Aug 10, 2015 at 3:09 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
>> wrote:
>> > On Thu, Aug 6, 2015 at 12:24 PM, Haribabu Kommi
>> > <kommi(dot)haribabu(at)gmail(dot)com>
>> > wrote:
>> >
>> > What is the configuration for test (RAM of m/c, shared_buffers,
>> > scale_factor, etc.)?
>>
>> Here are the details:
>>
>> CPU - 16 core, RAM - 252 GB
>>
>> shared_buffers - 1700MB, buffer_cache_ratio - 70
>> wal_buffers - 16MB, synchronous_commit - off
>> checkpoint_timeout - 15min, max_wal_size - 5GB.
>>
>> pgbench scale factor - 75 (1GB)
>>
>> Load test table size - 1GB
>
>
> It seems that test table can fit easily in shared buffers, I am not sure
> this patch will be of benefit for such cases, why do you think it can be
> beneficial for such cases?

Yes. This configuration combination is may not be best for the test.

The idea behind these setting is to provide enough shared buffers to cache
table by tuning the buffer_cache_ratio from 0 to 70% of shared buffers
So the cache tables have enough shared buffers and rest of the shared
buffers can be used for normal tables i.e load test table.

I will try to evaluate some more performance tests with different shared
buffers settings and load.

Regards,
Hari Babu
Fujitsu Australia