[Stgt-devel] sg_turs on stgt iscsi drive is very slow

[Ming Zhang]

On Tue, 2006-12-12 at 08:02 +0900, FUJITA Tomonori wrote:
> From: Ming Zhang <blackmagic02881 at gmail.com>
> Subject: [Stgt-devel] sg_turs on stgt iscsi drive is very slow
> Date: Mon, 11 Dec 2006 11:58:27 -0500
> 
> > Pulled out the linux-2.6-target git tree, compiled stgt and iet under
> > same kernel. Export a 4 disk raid0 device to ini. Ini is open-iscsi
> > r598.
> > 
> > Want to know how efficient stgt handle context switch. 
> > 
> > run  sg_turs -t -n=10000 /dev/sg0 on IET drive. results is 2521/sec.
> 
> With IET, several threads handle TUR. With stgt, the single thread
> handles TUR (synchronously). stgt asynchronously handles only I/O
> commands (READ, WRITE, etc), which are expected to be performed
> efficiently.

if i set Wthreads to 1 and "ps axu" to double check there is only 1
worker thread, i still get 5470 op/sec.

also when run stgt, the top show almost no cpu activity. 

> 
> So I don't think the results are related with context switch at all.

ok, it is not related to CS. but then why stgt is so slow?

it should be easy to reproduce this at u side. if u can not reproduce
this slowness, i will check my environment again. i clone u git tress
just yesterday.