linux-kernel - Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment

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Date:   Fri, 23 Dec 2016 09:33:36 +1100
From:   Dave Chinner <david@...morbit.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Jens Axboe <axboe@...com>, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Peter Anvin <hpa@...or.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [4.10, panic, regression] iscsi: null pointer deref at
 iscsi_tcp_segment_done+0x20d/0x2e0

On Fri, Dec 23, 2016 at 09:15:00AM +1100, Dave Chinner wrote:
> On Thu, Dec 22, 2016 at 01:10:19PM -0800, Linus Torvalds wrote:
> > Ok, so the numa issue was a red herring. With that fixed:
> > 
> > On Thu, Dec 22, 2016 at 1:06 PM, Dave Chinner <david@...morbit.com> wrote:
> > >
> > > Better, but still bad. average files/s is not up to 200k files/s,
> > > so still a good 10-15% off where it should be. xfs_repair is back
> > > down to 10-15% off where it should be, too. bulkstat still fires off
> > > a bad page reference count warning, iscsi still panics immediately.
> > 
> > Do you have CONFIG_BLK_WBT enabled, perhaps?
> 
> Ok, yes, that's enabled. Let me go turn it off and see what happens.

Numbers are still all over the place.

FSUse%        Count         Size    Files/sec     App Overhead
.....
     0     28800000            0     228175.5         21928812
     0     30400000            0     167880.5         39628229
     0     32000000            0     124289.5         41420925
     0     33600000            0     150577.9         35382318
     0     35200000            0     216535.4         16072628
     0     36800000            0     233414.4         11846654
     0     38400000            0     213812.0         13356633
     0     40000000            0     175905.7         53012015
     0     41600000            0     157028.7         34700794
     0     43200000            0     138829.1         50282461

And the average is now back down to 185k files/s. repair runtime is
unchanged and still 10-15% off...

I've got to run away for a few hours right now, but I'll retest the
4.9 + xfs for-next branch when I get back to see if the problem is
my curent config or whether there really is a perf problem lurking
somewhere....

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com