Extremely slow O_DIRECT about directio HOT 3 CLOSED

Remember that O_DIRECT does no buffering at all. If you want it to do buffering you need to provide it yourself. Upping the buffer_block in your example like this makes it run a lot faster.

buffer_block := directio.AlignedBlock(4 * 1024 * directio.BlockSize) // 16MB buffer

Another thing the OS is doing for you without O_DIRECT is read ahead, so if you set one go routine up to read and another to write you'll gain a bit more speed as those things can work in parallel again.

So I don't think it is a bug, it is just a pitfall of using O_DIRECT.

from directio.

I'm closing this as I don't think this is a bug in this library, just a pitfall of O_DIRECT. (See above for explanation).

from directio.

Thank you for answer! I will add read ahead to my code :)

from directio.