On Tue 22-11-16 10:56:51, Nikolay Borisov wrote:
>
>
> On 11/21/2016 07:31 AM, Michal Hocko wrote:
> > Hi,
> > I am sorry for a late response, but I was offline until this weekend. I
> > will try to get to this email ASAP but it might take some time.
>
> No worries. I did some further digging up and here is what I got, which
> I believe is rather strange:
>
> struct scan_control {
> nr_to_reclaim = 32,
> gfp_mask = 37880010,
> order = 0,
> nodemask = 0x0,
> target_mem_cgroup = 0xffff8823990d1400,
> priority = 7,
> may_writepage = 1,
> may_unmap = 1,
> may_swap = 0,
> may_thrash = 1,
> hibernation_mode = 0,
> compaction_ready = 0,
> nr_scanned = 0,
> nr_reclaimed = 0
> }
>
> Parsing: 37880010
> #define ___GFP_HIGHMEM 0x02
> #define ___GFP_MOVABLE 0x08
> #define ___GFP_IO 0x40
> #define ___GFP_FS 0x80
> #define ___GFP_HARDWALL 0x20000
> #define ___GFP_DIRECT_RECLAIM 0x400000
> #define ___GFP_KSWAPD_RECLAIM 0x2000000
>
> And initial_priority is 12 (DEF_PRIORITY). Given that nr_scanned is 0
> and priority is 7 this means we've gone 5 times through the do {} while
> in do_try_to_free_pages. Also total_scanned seems to be 0. Here is the
> zone which was being reclaimed :
>
> http://sprunge.us/hQBi
LRUs on that zones seem to be empty from a quick glance. kmem -z in the
crash can give you per zone counters much more nicely.
> So what's strange is that the softlockup occurred but then the code
> proceeded (as evident from the subsequent stack traces), yet inspecting
> the reclaim progress it seems rather sad (no progress at all)
Unless I have misread the data above it seems something has either
isolated all LRU pages for some time or there simply are none while the
reclaim is desperately trying to make some progress. In any case this
sounds less than a happy system...
--
Michal Hocko
SUSE Labs
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