Re: Speed up Clog Access by increasing CLOG buffers

On Mon, Apr 4, 2016 at 8:55 PM, Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>
wrote:

> On 04/01/2016 04:39 PM, Andres Freund wrote:
>
>> On April 1, 2016 10:25:51 PM GMT+02:00, Jesper Pedersen <
>> jesper(dot)pedersen(at)redhat(dot)com> wrote:
>>
>>> Hi,
>>>
>>> On 03/31/2016 06:21 PM, Andres Freund wrote:
>>>
>>>> On March 31, 2016 11:13:46 PM GMT+02:00, Jesper Pedersen
>>>>
>>> <jesper(dot)pedersen(at)redhat(dot)com> wrote:
>>>
>>>>
>>>> I can do a USE_CONTENT_LOCK run on 0003 if it is something for 9.6.
>>>>>
>>>>
>>>> Yes please. I think the lock variant is realistic, the lockless did
>>>>
>>> isn't.
>>>
>>>>
>>>>
>>> I have done a run with -M prepared on unlogged running 10min per data
>>> point, up to 300 connections. Using data + wal on HDD.
>>>
>>> I'm not seeing a difference between with and without USE_CONTENT_LOCK
>>> --
>>> all points are within +/- 0.5%.
>>>
>>> Let me know if there are other tests I can perform
>>>
>>
>> How do either compare to just 0002 applied?
>>
>>
> 0001 + 0002 compared to 0001 + 0002 + 0003 (either way) were pretty much
> the same +/- 0.5% on the HDD run.
>
>
I think the main reason why there is no significant gain shown in your
tests is that on the m/c where you are testing the contention due to
CLOGControlLock is not high enough that any reduction on the same will
help. To me, it is visible in some of the high-end machines like which
have 4 or more sockets. So, I think these results should be taken as an
indication that there is no regression in the tests performed by you.

Thanks for doing all the tests for these patches.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com