Messages in this thread | | | Date | Fri, 30 Oct 2015 11:38:30 +0100 | From | Michal Hocko <> | Subject | Re: [lkp] [mm, page_alloc] 43993977ba: +88% OOM possibility |
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On Fri 30-10-15 16:21:40, Huang, Ying wrote: > Michal Hocko <mhocko@kernel.org> writes: > > > On Wed 28-10-15 13:36:02, kernel test robot wrote: > >> FYI, we noticed the below changes on > >> > >> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master > >> commit 43993977baecd838d66ccabc7f682342fc6ff635 ("mm, page_alloc: > >> distinguish between being unable to sleep, unwilling to sleep and > >> avoiding waking kswapd") > >> > >> We found the OOM possibility increased 88% in a virtual machine with 1G memory. > > > > Could you provide dmesg output from this test? > > Sure, Attached.
I can only see a single allocation failure warning: kworker/u4:1: page allocation failure: order:0, mode:0x2204000
This is obviously a non sleeping allocation with ___GFP_KSWAPD_RECLAIM set. ___GFP_HIGH (aka access to memory reserves) is not required so a failure of such an allocation is something to be expected.
[ 2294.616369] Workqueue: btrfs-submit btrfs_submit_helper [ 2294.616369] 0000000000000000 ffff88000d38f5e0 ffffffff8173f84c 0000000000000000 [ 2294.616369] ffff88000d38f678 ffffffff811abaee 00000000ffffffff 000000010038f618 [ 2294.616369] ffff8800584e4148 00000000ffffffff ffff8800584e2f00 0000000000000001 [ 2294.616369] Call Trace: [ 2294.616369] [<ffffffff8173f84c>] dump_stack+0x4b/0x63 [ 2294.616369] [<ffffffff811abaee>] warn_alloc_failed+0x125/0x13d [ 2294.616369] [<ffffffff811aecce>] __alloc_pages_nodemask+0x7c9/0x915 [ 2294.616369] [<ffffffff811ecc7b>] kmem_getpages+0x91/0x155 [ 2294.616369] [<ffffffff811eef0d>] fallback_alloc+0x1cc/0x24c [ 2294.616369] [<ffffffff811eed32>] ____cache_alloc_node+0x151/0x160 [ 2294.616369] [<ffffffff811ef1ed>] __kmalloc+0xb0/0x134 [ 2294.616369] [<ffffffff8105d7a5>] ? sched_clock+0x9/0xb [ 2294.616369] [<ffffffff8187d929>] ? virtqueue_add+0x78/0x37f [ 2294.616369] [<ffffffff8187d929>] virtqueue_add+0x78/0x37f [ 2294.616369] [<ffffffff81114f72>] ? __lock_acquire+0x751/0xf55 [ 2294.616369] [<ffffffff8187dca6>] virtqueue_add_sgs+0x76/0x85
The patch you are referring shouldn't make any change in this path because alloc_indirect which I expect is the allocation failing here does: gfp &= ~(__GFP_HIGHMEM | __GFP_HIGH)
and that came in via b92b1b89a33c ("virtio: force vring descriptors to be allocated from lowmem").
Are there more failed allocations during the test? The subject would suggest so.
Thanks!
-- Michal Hocko SUSE Labs
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