Re: /proc/sys/vm/(max|min)-readahead effect????

[Martin Dalecki]

Roy Sigurd Karlsbakk wrote:
> 
> > I suspect the per-device readahead for IDE is limiting the
> > effect of vm_max_readahead ...
> 
> hm...
> 
> any way to avoid this? I mean... The readahead in vm is layered above the
> actual device, and should therefore not be limited... Am I right? You
> could do several device calls, and fake readahead, and probably get pretty
> much out of it.

He means the hardware device read ahead, which can be changed by using
hdparm -a 32 -A1 /dev/hda
for example.
The value of the read ahead one layer on top of it
(read_ahead array) can't have *any* impact on performance.