Messages in this thread | | | Date | Mon, 2 Nov 2015 08:45:43 +0100 | From | Michal Hocko <> | Subject | Re: [lkp] [mm, page_alloc] 43993977ba: +88% OOM possibility |
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On Mon 02-11-15 07:20:37, Huang, Ying wrote: > Michal Hocko <mhocko@kernel.org> writes: > > > 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. > > We done 24 tests for the commit and 24 tests for its parent. There is > no OOM in any test for the parent commit, but there are OOM in 21 tests > for this commit. This is what I want to say in the subject. Sorry for > confusing.
It would be interesting to see all the page allocation failure warnings (if they are different). Maybe other callers have relied on GFP_ATOMIC and access to memory reserves. The above path is not this case though. -- Michal Hocko SUSE Labs
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