Re: Extreme I/O latency

[Fredrik Tolf <fredrik@xxxxxxxxxxxxx>]

On Tue, 2 Oct 2012, Dave Chinner wrote:
> On Tue, Oct 02, 2012 at 05:25:53AM +0200, Fredrik Tolf wrote:
> > On Tue, 2 Oct 2012, Dave Chinner wrote:
> > > On Tue, Oct 02, 2012 at 03:53:08AM +0200, Fredrik Tolf wrote:
> > > What is a "simple IO operation"?
> > Sorry, what I meant by "simple" is mostly on the interface level.
> > Like, a single syscall (with far less than a page of data in the
> > case of read or write), or, in this case, reading a single mmap'ed
> > page.
> Which might be "simple" by themselves, but when an application is
> doing thousands of such operations a second, the result is far from
> simple....
Certainly; though I seem to be bad at communicating it, the point I was 
trying to make is that it is, from the point of view of userspace, 
individual calls that take extremely long, rather than total throughput 
being poor. :)
--

Fredrik Tolf