Re: [PATCH 7/8] writeback: sync old inodes first in background writeback

Minchan Kim
2010-07-25T12:03:57Z

On Sun, Jul 25, 2010 at 07:43:20PM +0900, KOSAKI Motohiro wrote:
> Hi
>
> sorry for the delay.
>
> > Will you be picking it up or should I? The changelog should be more or less
> > the same as yours and consider it
> >
> > Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> >
> > It'd be nice if the original tester is still knocking around and willing
> > to confirm the patch resolves his/her problem. I am running this patch on
> > my desktop at the moment and it does feel a little smoother but it might be
> > my imagination. I had trouble with odd stalls that I never pinned down and
> > was attributing to the machine being commonly heavily loaded but I haven't
> > noticed them today.
> >
> > It also needs an Acked-by or Reviewed-by from Kosaki Motohiro as it alters
> > logic he introduced in commit [78dc583: vmscan: low order lumpy reclaim also
> > should use PAGEOUT_IO_SYNC]
>
> My reviewing doesn't found any bug. however I think original thread have too many guess
> and we need to know reproduce way and confirm it.
>
> At least, we need three confirms.
> o original issue is still there?
> o DEF_PRIORITY/3 is best value?

I agree. Wu, how do you determine DEF_PRIORITY/3 of LRU?
I guess system has 512M and 22M writeback pages.
So you may determine it for skipping max 32M writeback pages.
Is right?

And I have a question of your below comment.

"As the default dirty throttle ratio is 20%, sync write&wait
will hardly be triggered by pure dirty pages"

I am not sure exactly what you mean but at least DEF_PRIOIRTY/3 seems to be
related to dirty_ratio. It always can be changed by admin.
Then do we have to determine magic value(DEF_PRIORITY/3) proportional to dirty_ratio?

--
Kind regards,
Minchan Kim