Re: [PATCH 2/2] libata: turn off NCQ if queue depth is adjusted to 1

[Jeff Garzik <jgarzik@pobox.com>]

Ric Wheeler wrote:
> Just thinking out loud, but it would be really helpful to get drive 
> vendor's a basic set of tests for Linux systems -  error handling, 
> performance, SMART features, etc - that would run natively on linux.
> We would need to get something really easy to deploy, like a live CD 
> image with the test suite that could be booted on a pc, to get into an 
> environment that is used to booting DOS based floppies...

Strongly agreed.

I know some people use DOS-based environments; I would prefer the 
following test environment:

Equip systems with NICs that can do wake-on-lan and PXE.  To initiate 
testing of a system, perform a PXE boot, which downloads a 
custom-compiled kernel and initrd over the net.  The kernel boots, sets 
up a test environment in either ramfs or nfs (or a combination thereof), 
and runs a "do everything" script which starts the tests specified by 
the network admin.

The tests performed should be in three classes:  (1) data and non-data 
tests performed over a "direct submit" interface like SG_IO, (2) data 
tests performed by directly accessing the block device, and (3) data 
tests performed by accessing data through a common filesystem [ext3 or 
whatever is popular].

It is already trivial to write tests for #2 and #3.  Tests in class #1 
may require some thought and complexity, such as using multiple threads, 
to achieve maximal use of command queueing features.  I'm not aware of 
any userspace interface that allows fine-grained control of TCQ (Jens 
correct me here), or even an interface that does not require multiple 
threads to submit multiple tasks simultaneously.

	Jeff