Re: [Bug #13726] fio sync read 4k block size 35% regression

[Wu Fengguang <fengguang.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

On Tue, Jul 07, 2009 at 02:06:42PM +0800, Zhang, Yanmin wrote:
> On Tue, 2009-07-07 at 02:01 +0200, Rafael J. Wysocki wrote:
> > This message has been generated automatically as a part of a report
> > of recent regressions.
> > 
> > The following bug entry is on the current list of known regressions
> > from 2.6.30.  Please verify if it still should be listed and let me know
> > (either way).
> > 
> > 
> > Bug-Entry	: http://bugzilla.kernel.org/show_bug.cgi?id=13726
> > Subject		: fio sync read 4k block size 35% regression
> > Submitter	: Zhang, Yanmin <yanmin_zhang-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> > Date		: 2009-07-01 11:25 (6 days old)
> > First-Bad-Commit: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=51daa88ebd8e0d437289f589af29d4b39379ea76
> > References	: http://lkml.org/lkml/2009/6/30/679
> > Handled-By	: Wu Fengguang <fengguang.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> Fengguang,
> 
> I'm still working on it now. The new testing against 2.6.31-rc2 is ongoing.
> fio sync/mmap read has new behavior. I did collect some data. But suddenly
> with new created data, the fio_sync_read_4k regression disappeared, while
> fio_mmap_read is still there. Originally, the testing and bisect were stable.
> Let me check what happens firstly.

OK, thank you for the update.

> Just update.
> 
> How did you test your new readahead patches before sending to LKML?

I run various workloads and check if the readahead traces are abnormal.
In this regression case, the readahead traces are in fact normal :)

Thanks,
Fengguang