From: Baoquan He <bhe@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: David Hildenbrand <david@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
akpm@linux-foundation.org, aarcange@redhat.com
Subject: Re: Memory hotplug softlock issue
Date: Thu, 15 Nov 2018 15:53:56 +0800 [thread overview]
Message-ID: <20181115075349.GL2653@MiWiFi-R3L-srv> (raw)
In-Reply-To: <20181115073052.GA23831@dhcp22.suse.cz>
On 11/15/18 at 08:30am, Michal Hocko wrote:
> On Thu 15-11-18 13:10:34, Baoquan He wrote:
> > On 11/14/18 at 04:00pm, Michal Hocko wrote:
> > > On Wed 14-11-18 22:52:50, Baoquan He wrote:
> > > > On 11/14/18 at 10:01am, Michal Hocko wrote:
> > > > > I have seen an issue when the migration cannot make a forward progress
> > > > > because of a glibc page with a reference count bumping up and down. Most
> > > > > probable explanation is the faultaround code. I am working on this and
> > > > > will post a patch soon. In any case the migration should converge and if
> > > > > it doesn't do then there is a bug lurking somewhere.
> > > > >
> > > > > Failing on ENOMEM is a questionable thing. I haven't seen that happening
> > > > > wildly but if it is a case then I wouldn't be opposed.
> > > >
> > > > Applied your debugging patches, it helps a lot to printing message.
> > > >
> > > > Below is the dmesg log about the migrating failure. It can't pass
> > > > migrate_pages() and loop forever.
> > > >
> > > > [ +0.083841] migrating pfn 10fff7d0 failed
> > > > [ +0.000005] page:ffffea043ffdf400 count:208 mapcount:201 mapping:ffff888dff4bdda8 index:0x2
> > > > [ +0.012689] xfs_address_space_operations [xfs]
> > > > [ +0.000030] name:"stress"
> > > > [ +0.004556] flags: 0x5fffffc0000004(uptodate)
> > > > [ +0.007339] raw: 005fffffc0000004 ffffc900000e3d80 ffffc900000e3d80 ffff888dff4bdda8
> > > > [ +0.009488] raw: 0000000000000002 0000000000000000 000000cb000000c8 ffff888e7353d000
> > > > [ +0.007726] page->mem_cgroup:ffff888e7353d000
> > > > [ +0.084538] migrating pfn 10fff7d0 failed
> > > > [ +0.000006] page:ffffea043ffdf400 count:210 mapcount:201 mapping:ffff888dff4bdda8 index:0x2
> > > > [ +0.012798] xfs_address_space_operations [xfs]
> > > > [ +0.000034] name:"stress"
> > > > [ +0.004524] flags: 0x5fffffc0000004(uptodate)
> > > > [ +0.007068] raw: 005fffffc0000004 ffffc900000e3d80 ffffc900000e3d80 ffff888dff4bdda8
> > > > [ +0.009359] raw: 0000000000000002 0000000000000000 000000cb000000c8 ffff888e7353d000
> > > > [ +0.007728] page->mem_cgroup:ffff888e7353d000
> > >
> > > I wouldn't be surprised if this was a similar/same issue I've been
> > > chasing recently. Could you try to disable faultaround to see if that
> > > helps. It seems that it helped in my particular case but I am still
> > > waiting for the final good-to-go to post the patch as I do not own the
> > > workload which triggered that issue.
> >
> > Tried, still stuck in last block sometime. Usually after several times
> > of hotplug/unplug. If stop stress program, the last block will be
> > offlined immediately.
>
> Is the pattern still the same? I mean failing over few pages with
> reference count jumping up and down between attempts?
->count jumping up and down, mapcount stays the same value.
>
> > [root@ ~]# cat /sys/kernel/debug/fault_around_bytes
> > 4096
>
> Can you make it 0?
I executed 'echo 0 > fault_around_bytes', value less than one page size
will round up to one page.
/*
* fault_around_bytes must be rounded down to the nearest page order as it's
* what do_fault_around() expects to see.
*/
static int fault_around_bytes_set(void *data, u64 val)
{
if (val / PAGE_SIZE > PTRS_PER_PTE)
return -EINVAL;
if (val > PAGE_SIZE)
fault_around_bytes = rounddown_pow_of_two(val);
else
fault_around_bytes = PAGE_SIZE; /* rounddown_pow_of_two(0) is undefined */
return 0;
}
next prev parent reply other threads:[~2018-11-15 7:54 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-14 7:09 Memory hotplug softlock issue Baoquan He
2018-11-14 7:16 ` Baoquan He
2018-11-14 8:18 ` David Hildenbrand
2018-11-14 9:00 ` Baoquan He
2018-11-14 9:25 ` David Hildenbrand
2018-11-14 9:41 ` Michal Hocko
2018-11-14 9:48 ` David Hildenbrand
2018-11-14 10:04 ` Michal Hocko
2018-11-14 9:01 ` Michal Hocko
2018-11-14 9:22 ` David Hildenbrand
2018-11-14 9:37 ` Michal Hocko
2018-11-14 9:39 ` David Hildenbrand
2018-11-14 14:52 ` Baoquan He
2018-11-14 15:00 ` Michal Hocko
2018-11-15 5:10 ` Baoquan He
2018-11-15 7:30 ` Michal Hocko
2018-11-15 7:53 ` Baoquan He [this message]
2018-11-15 8:30 ` Michal Hocko
2018-11-15 9:42 ` David Hildenbrand
2018-11-15 9:52 ` Baoquan He
2018-11-15 9:53 ` David Hildenbrand
2018-11-15 13:12 ` Baoquan He
2018-11-15 13:19 ` Michal Hocko
2018-11-15 13:23 ` Baoquan He
2018-11-15 14:25 ` Michal Hocko
2018-11-15 13:38 ` Baoquan He
2018-11-15 14:32 ` Michal Hocko
2018-11-15 14:34 ` Baoquan He
2018-11-16 1:24 ` Baoquan He
2018-11-16 9:14 ` Michal Hocko
2018-11-17 4:22 ` Baoquan He
[not found] ` <20181119105202.GE18471@MiWiFi-R3L-srv>
2018-11-19 12:40 ` Michal Hocko
2018-11-19 12:51 ` Michal Hocko
2018-11-19 14:10 ` Michal Hocko
2018-11-19 16:36 ` Vlastimil Babka
2018-11-19 16:46 ` Michal Hocko
2018-11-19 16:46 ` Vlastimil Babka
2018-11-19 16:48 ` Vlastimil Babka
2018-11-19 17:01 ` Michal Hocko
2018-11-19 17:33 ` Michal Hocko
2018-11-19 20:34 ` Hugh Dickins
2018-11-19 20:59 ` Michal Hocko
2018-11-20 1:56 ` Baoquan He
2018-11-20 5:44 ` Hugh Dickins
2018-11-20 13:38 ` Vlastimil Babka
2018-11-20 13:58 ` Baoquan He
2018-11-20 14:05 ` Michal Hocko
2018-11-20 14:12 ` Baoquan He
2018-11-21 1:21 ` Hugh Dickins
2018-11-21 1:08 ` Hugh Dickins
2018-11-21 3:20 ` Hugh Dickins
2018-11-21 17:31 ` Michal Hocko
2018-11-22 1:53 ` Hugh Dickins
2018-11-14 10:00 ` Michal Hocko
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