I've noticed that when I do heavy write applications, the whole system slows down. To test this further I ran this to do a (relatively) low-CPU, high disk activity:john -incremental > file_on_SSDThis pumps out tens of thousands of strings per second to a file on my system disk.When it's doing this, the mouse lags, TTYs become unresponsive, applications fade and generally the whole computer becomes unusable. When I can eventually Control+C john, the system comes back to full strength after a few seconds.This is an extreme example but I have similar issues with slightly less write-intensive activities like copying big files from fast sources or transcoding.My main OS disk is a quite fast SSD (OCZ Agility 60GB) with EXT4. If I write john's output to a mechanical disk with EXT4, I don't experience the same slow-downs though the rate is a lot slower (SSD does ~42,000 words per second, mechanical does 8,000 w/s). The throughput may be relevant. The mechanical disk also has nothing to do with the system. It's just data.And I'm using kernel 2.6.35-2 but I've noticed this issue since I got this SSD when I was probably using  .31 or something from around that time.So what's causing the slowdown? EXT4 issue? Kernel issue? SSD issue? All of the above? Something else?If you think I need to run an additional test, just drop a comment telling me what to do and I'll append the result to the question.
Heavy write activity on SSD nukes system performance
kernel;performance;io;ssd
This has been a known issue for awhile. Using an SSD-tuned FS like Btrfs might help, but it might not.Ultimately, it is a bug in the IO scheduler/memory management systems. Recently, there have been some patches that aim to address this issue. See Fixed: The Linux Desktop Responsiveness Problem?These patches may eventually make their way into the mainline kernel, but for now, you will probably have to compile your own kernel if you want to fix this issue.