Improving the CPU and latency performance of Amazon applications using AWS CodeGuru Profiler

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Improving the CPU and latency performance of Amazon applications using AWS CodeGuru Profiler

Amazon CodeGuru Profiler is a developer tool powered by machine learning (ML) that helps identify an application’s most expensive lines of code and provides intelligent recommendations to optimize it. You can identify application performance issues and troubleshoot latency and CPU utilization issues in your application.

You can use CodeGuru Profiler to optimize performance for any application running on AWS Lambda, Amazon Elastic Compute Cloud (Amazon EC2), Amazon Elastic Container Service (Amazon ECS), AWS Fargate, or AWS Elastic Beanstalk, and on premises.

This post gives a high-level overview of how CodeGuru Profiler has reduced CPU usage and latency by approximately 50% and saved around $100,000 a year for a particular Amazon retail service.

Technical and business value of CodeGuru Profiler

CodeGuru Profiler is easy and simple to use, just turn it on and start using it. You can keep it running in the background and you can just look into the CodeGuru Profiler findings and implement the relevant changes.

It’s fairly low cost and unlike traditional tools that take up lot of CPU and RAM, running CodeGuru Profiler has less than 1% impact on total CPU usage overhead to applications and typically uses no more than 100 MB of memory.

You can run it in a pre-production environment to test changes to ensure no impact occurs on your application’s key metrics.

It automatically detects performance anomalies in the application stack traces that start consuming more CPU or show increased latency. It also provides visualizations and recommendations on how to fix performance issues and the estimated cost of running inefficient code. Detecting the anomalies early prevents escalating the issue in production. This helps you prioritize remediation by giving you enough time to fix the issue before it impacts your service’s availability and your customers’ experience.

How we used CodeGuru Profiler at Amazon

Amazon has on-boarded many of its applications to CodeGuru Profiler, which has resulted in an annual savings of millions of dollars and latency improvements. In this post, we discuss how we used CodeGuru Profiler on an Amazon Prime service. A simple code change resulted in saving around $100,000 for the year.

Opportunity to improve

After a change to one of our data sources that caused its payload size to increase, we expected a slight increase to our service latency, but what we saw was higher than expected. Because CodeGuru Profiler is easy to integrate, we were able to quickly make and deploy the changes needed to get it running on our production environment.

After loading up the profile in Amazon CodeGuru Profiler, it was immediately apparent from the visualization that a very large portion of the service’s CPU time was being taken up by Jackson deserialization (37%, across the two call sites). It was also interesting that most of the blocking calls in the program (in blue) was happening in the jackson.databind method _createAndCacheValueDeserializer.

Flame graphs represent the relative amount of time that the CPU spends at each point in the call graph. The wider it is, the more CPU usage it corresponds to.

The following flame graph is from before the performance improvements were implemented.

The Flame Graph before the deployment

Looking at the source for _createAndCacheValueDeserializer confirmed that there was a synchronized block. From within it, _createAndCache2 was called, which actually did the adding to the cache. Adding to the cache was guarded by a boolean condition which had a comment that indicated that caching would only be enabled for custom serializers if @JsonCachable was set.

Solution

Checking the documentation for @JsonCachable confirmed that this annotation looked like the correct solution for this performance issue. After we deployed a quick change to add @JsonCachable to our four custom deserializers, we observed that no visible time was spent in _createAndCacheValueDeserializer.

Results

Adding a one-line annotation in four different places made the code run twice as fast. Because it was holding a lock while it recreated the same deserializers for every call, this was allowing only one of the four CPU cores to be used and therefore causing latency and inefficiency. Reusing the deserializers avoided repeated work and saved us lot of resources.

After the CodeGuru Profiler recommendations were implemented, the amount of CPU spent in Jackson reduced from 37% to 5% across the two call paths, and there was no visible blocking. With the removal of the blocking, we could run higher load on our hosts and reduce the fleet size, saving approximately $100,000 a year in Amazon EC2 costs, thereby resulting in overall savings.

The following flame graph shows performance after the deployment.

The Flame Graph after the deployment

Metrics

The following graph shows that CPU usage reduced by almost 50%. The blue line shows the CPU usage the week before we implemented CodeGuru Profiler recommendations, and green shows the dropped usage after deploying. We could later safely scale down the fleet to reduce costs, while still having better performance than prior to the change.

The following graph shows the server latency, which also dropped by almost 50%. The latency dropped from 100 milliseconds to 50 milliseconds as depicted in the initial portion of the graph. The orange line depicts p99, green p99.9, and blue p50 (mean latency).

Conclusion

With a few lines of changed code and a half-hour investigation, we removed the bottleneck which led to lower utilization of resources and  thus we were able to decrease the fleet size. We have seen many similar cases, and in one instance, a change of literally six characters of inefficient code, reduced CPU usage from 99% to 5%.

Across Amazon, CodeGuru Profiler has been used internally among various teams and resulted in millions of dollars of savings and performance optimization. You can use CodeGuru Profiler for quick insights into performance issues of your application. The more efficient the code and application is, the less costly it is to run. You can find potential savings for any application running in production and significantly reduce infrastructure costs using CodeGuru Profiler. Reducing fleet size, latency, and CPU usage is a major win.

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