Thank you for the reply, Matthew. I'm experimenting with GDAL and, in particular, working on improving the I/O performance of geo-applications. I wanted to get more control from the application over how the kernel handles I/O requests. But basically all the optimizations are hidden in readahead. Whatever requests are executed are all translated into readahead. It would be very useful to be able to evaluate the difference with more fine-grained control on the application side. -----Original Message----- From: Matthew Wilcox <willy@xxxxxxxxxxxxx> Sent: Donnerstag, 21. Oktober 2021 15:28 To: Nurgaliev, Azat <Azat.Nurgaliev@xxxxxx> Cc: linux-fsdevel@xxxxxxxxxxxxxxx Subject: Re: Turn off readahead completely On Thu, Oct 21, 2021 at 01:16:46PM +0000, Azat.Nurgaliev@xxxxxx wrote: > Hello everyone, > > I need to turn readahead off completely in order to do my experiments. > Is there any way to turn it off completely? > > Setting /sys/block/<dev>/queue/read_ahead_kb to 0 causes readahead to become 4kb. That's entirely intentional. What experiment are you actually trying to perform?
