Re: [Patch][WiP] Tweaked LRU for shared buffers

On 2/17/19 2:53 PM, Tomas Vondra wrote:
> On 2/17/19 2:14 PM, Едигарьев, Иван Григорьевич wrote:
>> Hi there. I was responsible for the benchmarks, and I would be glad to
>> make clear that part for you.
>>
>> On Sat, 16 Feb 2019 at 02:30, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>>> Interesting. Where do these numbers (5/8 and 1/8) come from?
>>
>> The first number came from MySQL realization of LRU algorithm
>> <https://dev.mysql.com/doc/refman/8.0/en/innodb-buffer-pool.html>
>> and the second from simple tuning, we've tried to change 1/8 a little,
>> but it didn't change metrics significantly.
>>
>>> That TPS chart looks a bit ... wild. How come the master jumps so much
>>> up and down? That's a bit suspicious, IMHO.
>>
>> Yes, it is. It would be great if someone will try to reproduce those results.
>>
>
> I'll try.
>

I've tried to reproduce this behavior, and I've done a quite extensive
set of tests on two different (quite different) machines, but so far I
have not observed anything like that. The results are attached, along
with the test scripts used.

I wonder if this might be due to pg_ycsb using random_zipfian, which has
somewhat annoying behavior for some parameters (as I've mentioned in a
separate thread). But that should affect all the runs, not just some
shared_buffers sizes.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
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