On Thu, Mar 18, 2021 at 12:27:44PM +0530, Shashidhar Patil wrote: > Hi Theodore, > I forgot to include two important details , the stack trace of > loop0 driver and sar output, which clearly nail the problem. > The losetup with Ubuntu16.05 does not have O_DIRECT support and we > were not aware of bypassing of journalling if > O_DIRECT combined with preallocated file scenario. Which version of the kernel are you using? The use of O_DIRECT for loop devices requires kernel and losetup support. (Also note that upstream developers really generally don't pay attention --- or support --- distribution kernels unless they work for the company for which you are paying $$$ for support, and Ubuntu 16.05 isn't even a Long-Term Support distribution.) My suggestion is to see if you can replicate the problem on a modern userspace with the latest kernel. And if not, then that's an object lesson about why using a antediluvian is not a great life choice. :-) Cheers, - Ted
