Hi ext4 mailing list members, I hope you can help me with a problem. I recently upgraded my main audio PC to Fedora FC15 and, at the same time, reformatted by root drive to ext4. Since this upgrade this, my system has high system latency which is causing my audio hardware (firewire) to experience buffer under-runs (XRUNs). This causes "unhandled xrun" errors and the audio software fails. My audio software (jackd) is running in realtime mode with SCHED_FIFO priority. I have been using latencytop (http://www.latencytop.org/) to try to understand what is causing the system latency. Typically my system runs with a max latency around 5ms. If i run a disk heavy operation (such as updatedb) I see a max latency of around 20ms. Around the time that jackd fails, I can see events like this with a latency of 40 - 120 ms: "writing buffer to disk (synchronous)" = "jbd2_journal_commit_transaction" Screenshot here http://dl.dropbox.com/u/3289905/latencytop.png My kernel version is Linux speedy.local 2.6.38.8-32.fc15.i686.PAE #1 SMP Mon Jun 13 19:55:27 UTC 2011 i686 i686 i386 GNU/Linu The ext4 drive is mounted with these options: /dev/sda4 on / type ext4 (rw,relatime,seclabel,barrier=1,data=ordered) I also tried mounting using using noatime and also using data=writeback options. Unfortunately neither of these parameters resolved the problem Could you give me any advice or ideas about how I could minimize this latency? Thanks! Andy -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
