Subject: Re: Speed up Clog Access by increasing CLOG buffers
To: Amit Kapila <amit.kapila16@gmail.com>
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Cc: Andres Freund <andres@anarazel.de>,
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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Message-ID: <5b4e50ff-02a7-2838-10e6-da758637338f@2ndquadrant.com>
Date: Wed, 7 Sep 2016 14:14:03 +0200
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On 09/07/2016 01:13 PM, Amit Kapila wrote:
> On Wed, Sep 7, 2016 at 1:08 AM, Tomas Vondra
> <tomas.vondra@2ndquadrant.com> wrote:
>> On 09/06/2016 04:49 AM, Amit Kapila wrote:
>>> On Mon, Sep 5, 2016 at 11:34 PM, Tomas Vondra
>>> <tomas.vondra@2ndquadrant.com> wrote:
>>>>
>>>>
>>>> On 09/05/2016 06:03 AM, Amit Kapila wrote:
>>>>>  So, in short we have to compare three
>>>>> approaches here.
>>>>>
>>>>> 1) Group mode to reduce CLOGControlLock contention
>>>>> 2) Use granular locking model
>>>>> 3) Use atomic operations
>>>>>
>>>>> For approach-1, you can use patch [1].  For approach-2, you can use
>>>>> 0001-Improve-64bit-atomics-support patch[2] and the patch attached
>>>>> with this mail.  For approach-3, you can use
>>>>> 0001-Improve-64bit-atomics-support patch[2] and the patch attached
>>>>> with this mail by commenting USE_CONTENT_LOCK.  If the third doesn't
>>>>> work for you then for now we can compare approach-1 and approach-2.
>>>>>
>>>>
>>>> OK, I can compile all three cases - but onl with gcc 4.7 or newer. Sadly
>>>> the 4-socket 64-core machine runs Debian Jessie with just gcc 4.6 and my
>>>> attempts to update to a newer version were unsuccessful so far.
>>>>
>>>
>>> So which all patches your are able to compile on 4-socket m/c?  I
>>> think it is better to measure the performance on bigger machine.
>>
>> Oh, sorry - I forgot to mention that only the last test (with
>> USE_CONTENT_LOCK commented out) fails to compile, because the functions
>> for atomics were added in gcc-4.7.
>>
> 
> No issues, in that case we can leave the last test for now and do it later.
> 

FWIW I've managed to compile a new GCC on the system (all I had to do
was to actually read the damn manual), so I'm ready to do the test once
I get a bit of time.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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