Archive for the ‘latency’ Category
Revealing Hidden Latency Patterns
Latency Heat Map Response time – or latency – is crucial to understand in detail, but many of the common presentations of this data hide important details and patterns. Latency heat maps are an effective way to reveal these. I often use tools that provide heat maps directly, but sometimes I have separate trace output [...]
In: heatmaps, latency, performance, visualizations
Off-CPU Performance Analysis
I’ve been exercising a new approach for examining application performance, which involves measuring high resolution off-CPU time that is synchronous to the workload. This reveals which code-paths are blocked and waiting while off-CPU, and for how long exactly. This differs from traditional profiling which often samples the activity of threads at a given interval, and [...]
In: DTrace, latency, mysql, off-cpu, performance
Breaking Down MySQL/Percona Query Latency With DTrace
In May I spoke at PerconaLive 2011 in New York, giving a talk titled “Breaking Down MySQL/Percona Query Latency With DTrace”. It was a great conference, and I’d recommend attending the next one if you get a chance. I also attended a number of the talks, and have also caught up on some via video [...]
In: DTrace, latency, mysql, performance, video
File System Latency: part 5
This is part 5 of File System Latency, a series on storage I/O performance from the application perspective (see parts 1, 2, 3 and 4). Previously I explained why disk I/O metrics may not reflect application performance, and how some file system issues may be invisible at the disk I/O level. I then showed how [...]
In: cloud analytics, DTrace, filesystem, latency, mysql, performance, vfsstat
File System Latency: part 4
This is part 4 on file system latency, a series on storage I/O performance from the application perspective (see part 1, part 2 and part 3). In the previous post I showed how to trace file system latency from within MySQL using the pid provider. In this post I’ll show how similar data can be [...]
In: DTrace, filesystem, latency, mysql, performance
File System Latency: part 3
This is part 3 on file system latency, a series on storage I/O performance from the application perspective (see part 1 and part 2). Here I’ll show how to actually measure file system I/O latency – the time spent waiting on the file system to complete I/O. Examining this can save a lot of time [...]
In: DTrace, filesystem, latency, mysql, performance
File System Latency: part 2
This is part 2 of File System Latency, a series on storage I/O performance from the application perspective. In the first part I explained why disk I/O is difficult to associate with an application, and why it can be altered from what the application requested. In this part I’ll focus more on the file system, [...]
In: DTrace, filesystem, latency, mysql, performance
File System Latency: part 1
When considering I/O performance from the perspective of applications, file systems can prove to be a better target for analysis than disks. With modern file systems using more DRAM-based cache and performing more asynchronous disk I/O, what the application experiences can vastly differ to what the disks are doing. I’ll demonstrate this by examining I/O [...]
In: DTrace, filesystem, latency, mysql, performance
