Re: [PATCH v2] virtio_balloon: disable oom killer when fill balloon

[Minchan Kim]

Please resend this with [2/2] to linux-mm.

On Tue, Apr 26, 2011 at 5:59 PM, Dave Young <hidave.darkstar@xxxxxxxxx> wrote:
> When memory pressure is high, virtio ballooning will probably cause oom killing.
> Even if alloc_page with GFP_NORETRY itself does not directly trigger oom it
> will make memory becoming low then memory alloc of other processes will trigger
> oom killing. It is not desired behaviour.

I can't understand why it is undesirable.
Why do we have to handle it specially?


>
> Here disable oom killer in fill_balloon to address this issue.
> Add code comment as KOSAKI Motohiro's suggestion.
>
> Signed-off-by: Dave Young <hidave.darkstar@xxxxxxxxx>
> ---
> Âdrivers/virtio/virtio_balloon.c | Â Â8 ++++++++
> Â1 file changed, 8 insertions(+)
>
> --- linux-2.6.orig/drivers/virtio/virtio_balloon.c   Â2011-04-26 11:39:14.053118406 +0800
> +++ linux-2.6/drivers/virtio/virtio_balloon.c  2011-04-26 16:54:56.419741542 +0800
> @@ -25,6 +25,7 @@
> Â#include <linux/freezer.h>
> Â#include <linux/delay.h>
> Â#include <linux/slab.h>
> +#include <linux/oom.h>
>
> Âstruct virtio_balloon
> Â{
> @@ -102,6 +103,12 @@ static void fill_balloon(struct virtio_b
> Â Â Â Â/* We can only do one array worth at a time. */
> Â Â Â Ânum = min(num, ARRAY_SIZE(vb->pfns));
>
> + Â Â Â /* Disable oom killer for indirect oom due to our memory consuming
> + Â Â Â Â* Currently only hibernation code use oom_killer_disable,

Hmm, Please look at current mmotm. Now oom_killer_disabled is used by
do_try_to_free_pages in mmotm so it could make unnecessary oom kill.

BTW, I can't understand why we need to handle virtio by special.
Could you explain it in detail? :)



-- 
Kind regards,
Minchan Kim
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