io scheduling / serializing io requests / readahead

io scheduling / serializing io requests / readahead

[Roy Sigurd Karlsbakk]

hi

Are there any ways to tell Linux to use some sort of readahead
functionality that'll give me the ability to schedule I/O more loosely, so
some 100 files can be read concurrently without ruining the system by
seeking all the time?

I've tried to alter /proc/sys/vm/(min|max)-readahead, but it doesn't have
any effect...

roy

--
Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA

Computers are like air conditioners.
They stop working when you open Windows.

Re: io scheduling / serializing io requests / readahead

[Andrew Morton]

Roy Sigurd Karlsbakk wrote:
> 
> hi
> 
> Are there any ways to tell Linux to use some sort of readahead
> functionality that'll give me the ability to schedule I/O more loosely, so
> some 100 files can be read concurrently without ruining the system by
> seeking all the time?

There's a new system call sys_readhead() which may provide what you
want.

A simple alternative is to just cat each file, one at a time
onto /dev/null before the application starts up.

> I've tried to alter /proc/sys/vm/(min|max)-readahead, but it doesn't have
> any effect...
> 

Yup.  We covered that in the other thread.