On Wed, Sep 16, 2015 at 06:12:29PM -0700, Linus Torvalds wrote: > On Wed, Sep 16, 2015 at 5:37 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote: > > > > TL;DR: Results look really bad - not only is the plugging > > problematic, baseline writeback performance has regressed > > significantly. > > Dave, if you're testing my current -git, the other performance issue > might still be the spinlock thing. I have the fix as the first commit in my local tree - it'll remain there until I get a conflict after an update. :) > The plugging IO pauses are interesting, though. Plugging really > *shouldn't* cause that kind of pauses, _regardless_ of what level it > happens on, so I wonder if the patch ends up just exposing some really > basic problem that just normally goes hidden. Right, that's what I suspect - it didn't happen on older kernels, but we've just completely reworked the writeback code for the control group awareness since I last looked really closely at this... > Can you match up the IO wait times with just *where* it is > waiting? Is it waiting for that inode I_SYNC thing in > inode_sleep_on_writeback()? I'll do some more investigation. > But it does sound like we should just revert the whole plugging for > now, if only because "it has odd effects". Yup - we can add it again next merge window once we get to the bottom of whatever is going on and have had time to test the new code properly. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
