> 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.
>
> Here disable oom killer in fill_balloon to address this issue.
>
> Signed-off-by: Dave Young <hidave.darkstar@xxxxxxxxx>
> ---
> drivers/virtio/virtio_balloon.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> --- linux-2.6.orig/drivers/virtio/virtio_balloon.c 2010-10-13 10:14:38.000000000 +0800
> +++ linux-2.6/drivers/virtio/virtio_balloon.c 2011-04-26 11:38:43.979785141 +0800
> @@ -25,6 +25,7 @@
> #include <linux/freezer.h>
> #include <linux/delay.h>
> #include <linux/slab.h>
> +#include <linux/oom.h>
>
> struct virtio_balloon
> {
> @@ -102,6 +103,7 @@ static void fill_balloon(struct virtio_b
> /* We can only do one array worth at a time. */
> num = min(num, ARRAY_SIZE(vb->pfns));
>
> + oom_killer_disable();
I think this patch need proper comment at least. My first impression
is, "Hm, __GFP_NORETRY should prevent oom, why is this necessary?".
So, this actually prevent _another_ thread call out_of_memory().
Also, Here doesn't have any exclusion against hibernation (ie another
oom_killer_disable() callsite). It should be described why lock is
unnecessary.
Thanks.
> for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
> struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY |
> __GFP_NOMEMALLOC | __GFP_NOWARN);
> @@ -119,6 +121,7 @@ static void fill_balloon(struct virtio_b
> vb->num_pages++;
> list_add(&page->lru, &vb->pages);
> }
> + oom_killer_enable();
>
> /* Didn't get any? Oh well. */
> if (vb->num_pfns == 0)
> --
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