Comment 228 for bug 620074

And to make a more general comment... This bug is impossible to solve, since it (once again) has degraded into somewhere for everybody to tunnel everything that relates to a system feeling sluggish. There could be at least 10 separate issues described in here, or more. And while some of these are surely things we could do better, some are also certainly expected behaviour. We are at least touching several file systems, mm issues, and io scheduler issues. I'm quite sure that some of the mentioned behaviour is completely due to ext3 sucking at fsync.

I'd LOVE to be able to look into this, but honestly I have no idea where to start. What I would also love is for someone to post a test case that actually works. This includes observed behaviour and a description of what you would EXPECT to see happen. Then we/I should be able to at least judge whether there's something we can do about it. Expecting a fully fluid system while having 100 threads writing data to the device is not reasonable, for instance. But if it behaves significantly worse than previous kernels, then there's still something to look into.