Re: [PATCH 9/9] ext3: do not throttle metadata and journal IO

[KAMEZAWA Hiroyuki]

On Wed, 22 Apr 2009 09:33:49 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:


> > And this should be probably strictly connected to the IO controller. If
> > we throttle or delay the dispatching/submission of some IO requests
> > without throttling the dirty pages rate a cgroup could completely waste
> > its own available memory with dirty (hard and slow to reclaim) pages.
> > 
> > That is in part the approach I used in io-throttle v12, adding a hook in
> > balance_dirty_pages_ratelimited_nr() to throttle the current task when
> > cgroup's IO limit are exceeded. Argh!
> > 
> > So, another proposal could be to re-add in io-throttle v14 the old hook
> > also in balance_dirty_pages_ratelimited_nr().
> > 
> > In this way io-throttle would:
> > 
> > - use page_cgroup infrastructure and page_cgroup->flags to encode the
> >   cgroup id that firstly dirtied a generic page
> > - account and opportunely throttle sync and writeback IO requests in
> >   submit_bio()
> > - at the same time throttle the tasks in
> >   balance_dirty_pages_ratelimited_nr() if the cgroup they belong has
> >   exhausted the IO BW (or quota, share, etc. in case of proportional BW
> >   limit)
> > 
> 
> IMHO, io-controller should just work as I/O subsystem as bdi. Now, per-bdi dirty_ratio
> is suppoted and it seems to work well.  
> 
> Can't we write a function like  bdi_writeout_fraction() ?;
> It will be a simple choice.
> 
One more thing, if you want dirty_ratio for throttoling I/O not for supporing page reclaim,
Something like task_dirty_limit() will be apporpriate.

Thanks,
-Kame

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/