On Tue, Apr 26, 2011 at 3:22 PM, KOSAKI Motohiro <[email protected]> wrote: >> On Tue, Apr 26, 2011 at 2:38 PM, KOSAKI Motohiro >> <[email protected]> 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. >> >> >> >> Here disable oom killer in fill_balloon to address this issue. >> >> >> >> Signed-off-by: Dave Young <[email protected]> >> >> --- >> >> 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(). >> >> Thanks, will fix. >> >> > Also, Here doesn't have any exclusion against hibernation (ie another >> > oom_killer_disable() callsite). It should be described why lock is >> > unnecessary. >> >> Good catch, but lock should better be handled in oom_killer_disable >> function itself, >> What do you think? >> >> For oom killer multi user there's more problem, if process A disable >> oom killer then Process B enable oom killer, it is not A want to see, >> Any thoughts? > > If baloon and hibernation don't have any implicit exclusion, you are > right.
For this case, hibernation will freeze balloon thread before call oom_killer_disable, so there's no problem. If we consider future users of oom_killer_disabled, we will have to deal with it. > > Sorry, I don't virtio internal. please don't ask me. > > > > -- Regards dave -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
