# Increased QPS erratic CPU behavior

**URL:** <https://discuss.elastic.co/t/increased-qps-erratic-cpu-behavior/11647>\
**Category:** Elasticsearch\
**Created:** [April 19, 2013, 7:01pm UTC](https://discuss.elastic.co/t/increased-qps-erratic-cpu-behavior/11647 "2013-04-19T19:01:41Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Jerome\_Gagnon](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jerome_gagnon/32/2178_2.png) [@Jerome\_Gagnon](https://discuss.elastic.co/u/Jerome_Gagnon)\
**Post date:** [April 19, 2013, 7:01pm UTC](https://discuss.elastic.co/t/increased-qps-erratic-cpu-behavior/11647/1 "2013-04-19T19:01:41Z")

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Hi !

I'm actually testing ElasticSearch 0.90.x and go very  
erratic behavior while increasing query rate. We are running many  
benchmarks to push the 2 nodes cluster to the limit, with our standard  
query which is consistent mainly of a querystring + terms filter.

Basically, when we run the cluster at a query rate of \<26 everything seems  
fine, the cpu usage is at ~50%, no iowait at all and pretty decent response  
time (~150ms). But thats when we go up to 27 QPS, the CPU usage seems to go  
through the roof (100%), still no IO wait but the response time goes up to  
1000ms.

While doing some CPU profiling, we noticed that the FixedBitSet methods  
(or, and, ) usage seems to have grown a lot (about 10x more). The 2  
cpu snapshots are attached to this message.

So, how come that an increase of 1 query per second can completely  
overwhelm the cluster like that ? There is nothing else changed, only an  
increase of the rate into our benchmark. This seems like a weird behavior  
and it's kind of blocking at the moment.

--  
Jérôme Gagnon

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [July 6, 2017, 2:40am UTC](https://discuss.elastic.co/t/increased-qps-erratic-cpu-behavior/11647/2 "2017-07-06T02:40:19Z")

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Closed on July 6, 2017, 2:40am UTC