Thanks for the pointer! Actually, I am interested in disabling kernel readahead in order to do some experiment. So, is there any fast way to do that? On Fri, Apr 12, 2002 at 02:46:47AM -0700, Sharath wrote: > guys.. guys.. do not mistake the kernel read ahead > with the disk's... > > the harddisk contains a buffer (256k in mine and 1 mb > in the newer models).. when a read request is issued > to the disk, the disks logic decides which sectors to > 'buffer'... this data is stored in the HDs internal > buffer.. and not transferred to the system's memory.. > the disk's read ahead and is not controlled but the > OS. > > the kernel has its own buffers to store IO. The kernel > would be left to decide which sectors to read into > these regions. If the process is IO bound and is > reading a file, the kernel can predict the next read > and 'prepare' for it (look into inode entries and > determine where the next data recides) before the > actual read call occurs. This is the kernels > readahead. > > Ideally, they shouldn't be disabled. I have got some > of the best performance with full utilization of my > disk capabilities.. > > but don't have a clue on which algorithmn the kernel > uses.. but this is twisting the matters a little.. > > but the bottom line is: hdparam is different from what > the kernel does.. DO NOT mistake them -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
