Mailing-List: contact dev-help@cassandra.apache.org; run by ezmlm
Precedence: bulk
Reply-To: dev@cassandra.apache.org
Received-SPF: pass (nike.apache.org: domain of belliottsmith@datastax.com
 designates 209.85.223.169 as permitted sender)
MIME-Version: 1.0
In-Reply-To: <JIRA.12696354.1392929997746.120319.1393534699454@arcas>
References: <JIRA.12696354.1392929997746@arcas>
	<JIRA.12696354.1392929997746.120319.1393534699454@arcas>
Date: Thu, 27 Feb 2014 21:06:49 +0000
Message-ID: 
 <CAFqWSgeBmz=Kt1puqjQKqSpbuXmmLAzrbKs0xk1ehEJWX6Hn4w@mail.gmail.com>
Subject: Re: [jira] [Commented] (CASSANDRA-6746) Reads have a slow ramp up in
 speed
From: Benedict Elliott Smith <belliottsmith@datastax.com>
To: dev@cassandra.apache.org
Content-Type: multipart/alternative; boundary=047d7bd760c22cf39204f369b3e9

--047d7bd760c22cf39204f369b3e9
Content-Type: text/plain; charset=ISO-8859-1

I've been investigating this, but a bit slowly as was looking in the wrong
place. I haven't yet confirmed, but I have a strong suspicion of the
problem. Could you confirm the total physical memory on the nodes? If 8gb
or less, try applying the not yet committed patches in CASSANDRA-6692
(atomic b tree improvements), and setting the memtable_cleanup_threshold to
0.2, if you are looking at this today. I suspect it will fix it, although
if so it doesn't quite adequately explain the behaviour exactly. If you let
me know the cluster you're using I can test the same environment to make
sure I'm testing like for like as well.
On 27 Feb 2014 20:58, "Ryan McGuire (JIRA)" <jira@apache.org> wrote:

>
>     [
> https://issues.apache.org/jira/browse/CASSANDRA-6746?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13915038#comment-13915038]
>
> Ryan McGuire commented on CASSANDRA-6746:
> -----------------------------------------
>
> I tried re-running this with a 'nodetool flush' on each node after it's
> done with the write. It looked the same as above. I'm running a test with a
> 5 minute wait between the write and read to see if that causes a change.
>
> > Reads have a slow ramp up in speed
> > ----------------------------------
> >
> >                 Key: CASSANDRA-6746
> >                 URL:
> https://issues.apache.org/jira/browse/CASSANDRA-6746
> >             Project: Cassandra
> >          Issue Type: Bug
> >          Components: Core
> >            Reporter: Ryan McGuire
> >            Assignee: Benedict
> >              Labels: performance
> >             Fix For: 2.1 beta2
> >
> >         Attachments: 2.1_vs_2.0_read.png
> >
> >
> > On a physical four node cluister I am doing a big write and then a big
> read. The read takes a long time to ramp up to respectable speeds.
> > !2.1_vs_2.0_read.png!
> > [See data here|
> http://ryanmcguire.info/ds/graph/graph.html?stats=stats.2.1_vs_2.0_vs_1.2.retry1.json&metric=interval_op_rate&operation=stress-read&smoothing=1
> ]
>
>
>
> --
> This message was sent by Atlassian JIRA
> (v6.1.5#6160)
>

--047d7bd760c22cf39204f369b3e9--