linux-kernel - Re: Widespread crashes in -next, bisected to 'mm: drop HASH

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Date:   Sat, 20 May 2017 09:26:34 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     linux-kernel@...r.kernel.org,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Kevin Hilman <khilman@...libre.com>
Subject: Re: Widespread crashes in -next, bisected to 'mm: drop HASH_ADAPT'

On Fri 19-05-17 09:46:23, Guenter Roeck wrote:
> Hi,
> 
> my qemu tests of next-20170519 show the following results:
> 	total: 122 pass: 30 fail: 92
> 
> I won't bother listing all of the failures; they are available at
> http://kerneltests.org/builders. I bisected one (openrisc, because
> it gives me some console output before dying). It points to
> 'mm: drop HASH_ADAPT' as the culprit. Bisect log is attached.
> 
> A quick glance suggests that 64 bit kernels pass and 32 bit kernels fail.
> 32-bit x86 images fail and should provide an easy test case.

Hmm, this is quite unexpected as the patch is not supposed to change
things much. It just removes the flag and perform the new hash scaling
automatically for all requeusts which do not have any high limit.
Some of those didn't have HASH_ADAPT before but that shouldn't change
the picture much. The only thing that I can imagine is that what
formerly failed for early memblock allocations is now suceeding and that
depletes the early memory. Do you have any serial console from the boot?
-- 
Michal Hocko
SUSE Labs