Re: Do you know the reason for increased max latency due to xlog scaling?

From: "MauMau" <maumau307(at)gmail(dot)com>
To: "Andres Freund" <andres(at)2ndquadrant(dot)com>
Cc: "Heikki Linnakangas" <hlinnakangas(at)vmware(dot)com>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Do you know the reason for increased max latency due to xlog scaling?
Date: 2014-02-18 11:49:06
Message-ID: 0BDD0493C4A141F597ED6C1AF1E792E5@maumau
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-hackers

From: "Andres Freund" <andres(at)2ndquadrant(dot)com>
> On 2014-02-18 01:35:52 +0900, MauMau wrote:
>> For example, please see the max latencies of test set 2 (PG 9.3) and test
>> set 4 (xlog scaling with padding). They are 207.359 and 1219.422
>> respectively. The throughput is of course greatly improved, but I think
>> the
>> response time should not be sacrificed as much as possible. There are
>> some
>> users who are sensitive to max latency, such as stock exchange and online
>> games.
>
> You need to compare both at the same throughput to have any meaningful
> comparison.

I'm sorry for my lack of understanding, but could you tell me why you think
so? When the user upgrades to 9.4 and runs the same workload, he would
experience vastly increased max latency --- or in other words, greater
variance in response times. With my simple understanding, that sounds like
a problem for response-sensitive users.

Regards
MauMau

In response to

Responses

Browse pgsql-hackers by date

  From Date Subject
Next Message Andres Freund 2014-02-18 12:00:58 Re: Do you know the reason for increased max latency due to xlog scaling?
Previous Message MauMau 2014-02-18 11:35:02 Re: Memory ordering issue in LWLockRelease, WakeupWaiters, WALInsertSlotRelease