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From Shawn Heisey <s...@elyograg.org>
Subject Re: Long ParNew GC pauses - even when young generation is small
Date Sun, 20 Jan 2013 21:41:50 GMT
On 1/20/2013 2:13 PM, Markus Jelsma wrote:
> Hi Shawn,
>
> Although our heap spaces are much less than yours (256M for 2x 2.5GB cores per node)
we saw decreased throughput and higher latency with G1 on Java 6. You can also expect higher
CPU consumption. You can check it very well with VisualVM attached.
>
> Looking forward to your results.

I don't have any really good test tools developed for testing throughput 
and latency.  I have some less-than-ideal tools for other purposes that 
I might be able to adapt.

Throughput is not a major issue for us - query volume is quite low.  I 
would be mildly surprised by 5 queries per second.  I don't have much of 
an idea of queries per second over the short term - the numbers 
available in 3.5 are limited.

As for latency, early indications from an old SOLR-1972 patch suggest 
that the QTime values might be a little higher.  The primary server 
stats (using CMS/ParNew) are over 1 million queries, and the secondary 
server stats (using G1) so far are only about 5000 queries.  The QTime 
values are steadily dropping as the number of queries goes up.

Here's a status page that gathers all the stats.  Chain A is using 
CMS/ParNew and is no longer receiving queries.  All the queries are now 
going to chain B, which is using G1.

http://dl.dropbox.com/u/97770508/g1-vs-cms-stats.png

The server CPU utilization graph doesn't have enough information yet to 
make any determination, but what little data is visible suggests that 
CPU may be higher.  The secondary servers also have slightly slower CPUs 
than the primary servers.  I was forced to make concessions on later 
purchases to keep the cost down.

Thanks,
Shawn


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