Re: [PATCH] Negative (setpoint-dirty) in bdi_position_ratio()

From: Jan Kara
Date: Thu Jan 24 2013 - 10:16:00 EST


On Thu 24-01-13 22:57:07, Wu Fengguang wrote:
> Hi Paul,
>
> > (This patch does not solve the PAE OOM issue.)
>
> You may try the below debug patch. The only way the writeback patches
> should trigger OOM, I think, is for the number of dirty/writeback
> pages going out of control.
>
> Or more simple, you may show us the OOM dmesg which will contain the
> number of dirty pages. Or run this in a continuous loop during your
> tests, and see how the dirty numbers change before OOM:
I think he found the culprit of the problem being min_free_kbytes was not
properly reflected in the dirty throttling. But the patch has been already
picked up by Andrew so I didn't forward it to you. Paul please correct me
if I'm wrong.

Honza

>
> while :
> do
> grep -E '(Dirty|Writeback)' /proc/meminfo
> sleep 1
> done
>
> Thanks,
> Fengguang
>
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 50f0824..cf1165a 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1147,6 +1147,16 @@ pause:
> if (task_ratelimit)
> break;
>
> + if (nr_dirty > dirty_thresh + dirty_thresh / 2) {
> + if (printk_ratelimit())
> + printk(KERN_WARNING "nr_dirty=%lu dirty_thresh=%lu task_ratelimit=%lu dirty_ratelimit=%lu pos_ratio=%lu\n",
> + nr_dirty,
> + dirty_thresh,
> + task_ratelimit,
> + dirty_ratelimit,
> + pos_ratio);
> + }
> +
> /*
> * In the case of an unresponding NFS server and the NFS dirty
> * pages exceeds dirty_thresh, give the other good bdi's a pipe
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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