The Phoronix Test Suite is also capable of monitoring the CPU usage, Iowait, and other system sensors and metrics while the testing is taking place. To look at the impact particularly when using zlib compression with Btrfs due to the additional CPU overhead we used the Phoronix Test Suite's system monitor module as we ran Dbench with 128 clients, IOzone 2GB reads, and then PostMark. Below are the Phoronix Test Suite's recordings of the CPU usage during these three benchmarks.
To no surprise Btrfs with compression enabled had the highest CPU usage with the dual-core Intel Atom 330 being 13% more utilized than with Btrfs and no zlib compression. To some surprise though, when comparing EXT4 and Btrfs, Btrfs had a slightly lower CPU utilization rate than the evolutionary EXT4.
On average Btrfs with transparent compression enabled led to the lowest iowait and it also peaked much lower than EXT4 and Btrfs.
With these new file-system benchmarks against the latest Linux 2.6.33 kernel, Btrfs did remarkably well and continued to have more wins than even with the recent Linux 2.6.32 kernel. Btrfs pulled its wins with Dbench, FS-Mark, and the Threaded I/O Tester. Btrfs lost to EXT4 with PostgreSQL, Iozone write performance, Iozone read performance too except when compression was enabled, and PostMark except when using the file-system's transparent compression. Using the transparent zlib compression was of advantage in many of the benchmarks, but with only modestly taxing the CPU (+13% for an Intel Atom). We will be looking closer at the Btrfs zlib compression performance in a forthcoming article when we look in detail at what it has to offer for netbook users. There is also the Btrfs SSD mode for greater tuning.