Extreme I/O latency

[Fredrik Tolf]

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