Re: Speed up Clog Access by increasing CLOG buffers

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От Tomas Vondra
Тема Re: Speed up Clog Access by increasing CLOG buffers
Дата
Msg-id d7a7e096-daac-9207-8eae-50f450203312@2ndquadrant.com
обсуждение исходный текст
Ответ на Re: Speed up Clog Access by increasing CLOG buffers  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
Ответы Re: Speed up Clog Access by increasing CLOG buffers  (Robert Haas <robertmhaas@gmail.com>)
Список pgsql-hackers
On 09/26/2016 08:48 PM, Tomas Vondra wrote:
> On 09/26/2016 07:16 PM, Tomas Vondra wrote:
>>
>> The averages (over the 10 runs, 5 minute each) look like this:
>>
>>  3.2.80                 1      8     16     32     64    128    192
>> --------------------------------------------------------------------
>>  granular-locking    1567  12146  26341  44188  43263  49590  15042
>>  no-content-lock     1567  12180  25549  43787  43675  51800  16831
>>  group-update        1550  12018  26121  44451  42734  51455  15504
>>  master              1566  12057  25457  42299  42513  42562  10462
>>
>>  4.5.5                  1      8     16     32     64    128    192
>> --------------------------------------------------------------------
>>  granular-locking    3018  19031  27394  29222  32032  34249  36191
>>  no-content-lock     2988  18871  27384  29260  32120  34456  36216
>>  group-update        2960  18848  26870  29025  32078  34259  35900
>>  master              2984  18917  26430  29065  32119  33924  35897
>>

So, I got the results from 3.10.101 (only the pgbench data), and it 
looks like this:
 3.10.101               1      8     16     32     64    128    192
-------------------------------------------------------------------- granular-locking    2582  18492  33416  49583
53759 53572  51295 no-content-lock     2580  18666  33860  49976  54382  54012  51549 group-update        2635  18877
33806 49525  54787  54117  51718 master              2630  18783  33630  49451  54104  53199  50497
 

So 3.10.101 performs even better tnan 3.2.80 (and much better than 
4.5.5), and there's no sign any of the patches making a difference.

It also seems there's a major regression in the kernel, somewhere 
between 3.10 and 4.5. With 64 clients, 3.10 does ~54k transactions, 
while 4.5 does only ~32k - that's helluva difference.

I wonder if this might be due to running the benchmark on unlogged 
tables (and thus not waiting for WAL), but I don't see why that should 
result in such drop on a new kernel.

In any case, this seems like an issue unrelated to the patch, so I'll 
post further data into a new thread instead of hijacking this one.

regards

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



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