"It looks to be about 2.1% increase in time to do the make/mount/unmount operations with the marker patches in place and no blktrace operations," Alan Brunelle summarized some benchmarks testing the overhead of the kernel markers patches. He continued, "with the blktrace operations in place we see about a 3.8% decrease in time to do the same ops." Block layer maintainer Jens Axboe responded favorably, "thanks for running these numbers. I don't think you have to bother with it more. My main concern was a performance regression, increasing the overhead of running blktrace." He added, "I'd say the above is Good Enough for me," acking the kernel marker patches.
Jens went on to muse, "I do wonder about that performance _increase_ with blktrace enabled. I remember that we have seen and discussed something like this before, it's still a puzzle to me..." Mathieu Desnoyers agreed, "interesting question indeed," going on to suggest possible future tests to understand the unexpected performance increase.
blktrace is a block layer IO tracing tool for providing detailed information about request queue operations, originally developed by Jens Axboe and merged into the mainline kernel in 2.6.17-rc1.
Jens Axboe has been involved with Linux since 1993. 30 years old, he lives in Copenhagen, Denmark, and works as a Linux Kernel developer for Oracle. His block layer rewrite launched the 2.5 kernel development branch, a layer he continues to maintain and improve. Interested in most anything dealing with IO, he has introduced several new IO schedulers to the kernel, including the default CFQ, or Complete Fair Queuing scheduler.
In this interview, Jens talks about how he got interested in Linux, how he became the maintainer of the block layer and other block devices, and what's involved in being a maintainer. He describes his work on IO schedulers, offering an indepth look at the design and current status of the CFQ scheduler, including a peek at what's in store for the future. He conveys his excitement about the new splice IO model, explaining how it came about and how it works. And he discusses the current 2.6 kernel development process, the impact of git, and why the GPL is important to him.