[Devel] Re: seems to be a flaw in cfq

[Jens Axboe]

On Tue, Dec 19 2006, Jens Axboe wrote:
> On Tue, Dec 19 2006, Vasily Tarasov wrote:
> > ello, Jens.
> > 
> > Seems, that we've found some problem in CFQ.
> > I used your fio tool of version 1.9 to reproduce it.
> > 2.6.18 vanilla kernel.
> 
> I'll look over this report - in the mean time, can you see if the same
> situation exists in 2.6.19 and 2.6.20-rc1? Would help a lot!

I just tried to reproduce it in a recent kernel, and it does show
something very close to what you reported. Using 5 threads, 2 of them
sharing the same file, the 3 first threads get 6067 -> 6182KiB/sec each,
and the two threads sharing a file get 975KiB/sec each. That's really
bizarre, I'll take a good look at this! Thanks for reporting it.

-- 
Jens Axboe