Re: async I/O seems to be blocking on 2.6.15

[Brent Baccala <cosine@freesoft.org>]

On Sun, 5 Nov 2006, Jens Axboe wrote:

> On Fri, Nov 03 2006, Brent Baccala wrote:
>>
>> Does 7 microseconds seem a bit excessive for an io_submit (and a
>> gettimeofday)?
>
> I guess you mean miliseconds, not microseconds. 7 miliseconds seems way
> too long. I repeated your test here, and the 100 submits take 97000
> microseconds here - or 97 miliseconds. So that's a little less than 1
> msec per io_submit. Still pretty big. You can experiment with oprofile
> to profile where the kernel spends its time in that period.
>
> -- 
> Jens Axboe
>

Yes, of course, milliseconds.  I have enough other problems with this
program (measured in minutes, and no mistake that) that I doubt I'll
be profiling the kernel any time soon, but thank you for your help.

More than anything else, you've made me understand that I can't just
fire off a bunch of async requests like I'm tossing peanuts across the
table.  I've really got to pay attention to what's in that kernel
queue and how it gets managed.



 					-bwb

 					Brent Baccala
 					cosine@freesoft.org