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Re: testing HS/SR - 1 vs 2 performance

From: "Erik Rijkers" <er(at)xs4all(dot)nl>
To: "Simon Riggs" <simon(at)2ndQuadrant(dot)com>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Heikki Linnakangas" <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: testing HS/SR - 1 vs 2 performance
Date: 2010-04-22 18:39:14
Message-ID: d5a7014dc00b609f19804608d6f070b2.squirrel@webmail.xs4all.nl (view raw or flat)
Thread:
Lists: pgsql-hackers
On Sun, April 18, 2010 13:01, Simon Riggs wrote:
>>
>> OK, I'll put a spinlock around access to the head of the array.
>
> v2 patch attached
>

knownassigned_sortedarray.v2.diff applied to cvs HEAD (2010.04.21 22:36)

I have done a few smaller tests (scale 500, clients 1, 20):

init:
  pgbench -h /tmp -p 6565 -U rijkers -i -s 500 replicas


4x primary, clients 1:
scale: 500     clients:  1  tps = 11496.372655  pgbench -p 6565 -n -S -c 1 -T 900 -j 1
scale: 500     clients:  1  tps = 11580.141685  pgbench -p 6565 -n -S -c 1 -T 900 -j 1
scale: 500     clients:  1  tps = 11478.294747  pgbench -p 6565 -n -S -c 1 -T 900 -j 1
scale: 500     clients:  1  tps = 11741.432016  pgbench -p 6565 -n -S -c 1 -T 900 -j 1

4x standby, clients 1:
scale: 500     clients:  1  tps =   727.217672  pgbench -p 6566 -n -S -c 1 -T 900 -j 1
scale: 500     clients:  1  tps =   785.431011  pgbench -p 6566 -n -S -c 1 -T 900 -j 1
scale: 500     clients:  1  tps =   825.291817  pgbench -p 6566 -n -S -c 1 -T 900 -j 1
scale: 500     clients:  1  tps =   868.107638  pgbench -p 6566 -n -S -c 1 -T 900 -j 1


4x primary, clients 20:
scale: 500     clients: 20  tps = 34963.054102  pgbench -p 6565 -n -S -c 20 -T 900 -j 1
scale: 500     clients: 20  tps = 34818.985407  pgbench -p 6565 -n -S -c 20 -T 900 -j 1
scale: 500     clients: 20  tps = 34964.545013  pgbench -p 6565 -n -S -c 20 -T 900 -j 1
scale: 500     clients: 20  tps = 34959.210687  pgbench -p 6565 -n -S -c 20 -T 900 -j 1

4x standby, clients 20:
scale: 500     clients: 20  tps =  1099.808192  pgbench -p 6566 -n -S -c 20 -T 900 -j 1
scale: 500     clients: 20  tps =   905.926703  pgbench -p 6566 -n -S -c 20 -T 900 -j 1
scale: 500     clients: 20  tps =   943.531989  pgbench -p 6566 -n -S -c 20 -T 900 -j 1
scale: 500     clients: 20  tps =  1082.215913  pgbench -p 6566 -n -S -c 20 -T 900 -j 1


This is the same behaviour (i.e. extreme slow standby) that I saw earlier (and which caused the
original post, btw).  In that earlier instance, the extreme slowness disappeared later, after many
hours maybe even days (without bouncing either primary or standby).

I have no idea what could cause this; is no one else is seeing this ?

(if I have time I'll repeat on other hardware in the weekend)

any comment is welcome...


Erik Rijkers




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