Re: kswapd craziness round 2

[Daniel J Blueman]

On 18/02/2013 19:42, Hillf Danton wrote:
> On Mon, Feb 18, 2013 at 2:18 PM, Daniel J Blueman
> <daniel@xxxxxxxxxxxxxxxxxx> wrote:
> > On Monday, 18 February 2013 06:10:02 UTC+8, Jiri Slaby  wrote:
> >
> > > Hi,
> > >
> > > You still feel the sour taste of the "kswapd craziness in v3.7" thread,
> > > right? Welcome to the hell, part two :{.
> > >
> > > I believe this started happening after update from
> > > 3.8.0-rc4-next-20130125 to 3.8.0-rc7-next-20130211. The same as before,
> > > many hours of uptime are needed and perhaps some suspend/resume cycles
> > > too. Memory pressure is not high, plenty of I/O cache:
> > > # free
> > >               total       used       free     shared    buffers     cached
> > > Mem:       6026692    5571184     455508          0     351252    2016648
> > > -/+ buffers/cache:    3203284    2823408
> > > Swap:            0          0          0
> > >
> > > kswap is working very toughly though:
> > > root       580  0.6  0.0      0     0 ?        S    Ãno12  46:21 [kswapd0]
> > >
> > > This happens on I/O activity right now. For example by updatedb or find
> > > /. This is what the stack trace of kswapd0 looks like:
> > > [<ffffffff8113c431>] shrink_slab+0xa1/0x2d0
> > > [<ffffffff8113ecd1>] kswapd+0x541/0x930
> > > [<ffffffff810a3000>] kthread+0xc0/0xd0
> > > [<ffffffff816beb5c>] ret_from_fork+0x7c/0xb0
> > > [<ffffffffffffffff>] 0xffffffffffffffff
> >
> > Likewise with 3.8-rc, I've been able to reproduce [1] a livelock scenario
> > which hoses the box and observe RCU stalls [2].
> >
> > There may be a connection; I'll do a bit more debugging in the next few
> > days.
> >
> > Daniel
> >
> > --- [1]
> >
> > 1. live-booted image using ramdisk
> > 2. boot 3.8-rc with <16GB memory and without swap
> > 3. run OpenMP NAS Parallel Benchmark dc.B against local disk (ie not
> > ramdisk)
> > 4. observe hang O(30) mins later
> >
> > --- [2]
> >
> > [ 2675.587878] INFO: rcu_sched self-detected stall on CPU { 5}  (t=24000
> > jiffies g=6313 c=6312 q=68)
>
> Does Ingo's revert help? https://lkml.org/lkml/2013/2/15/168

Close, but no cigar; I still hit this livelock on 3.8-rc7 with Ingo's 
revert or Linus's fix.

However, I am unable to reproduce the hang with 3.7.9, so will begin 
bisection tomorrow, probably automating via pexpect.

Thanks,
  Daniel
--
Daniel J Blueman
Principal Software Engineer, Numascale Asia
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/