Hi Andy, On 07/12/2011 08:07 AM, Andy Campbell wrote: > 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 I guess the reason may be some regression. I have sent a patch to linux-ext4 with the subject "jbd/2[stable only]: Use WRITE_SYNC_PLUG in journal_commit_transaction." Can you try it to see if it helps. > > 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 Thanks Tao -- 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
