RE: [BUG] Page allocation failures with newest kernels

From: Yehuda Yitschak
Date: Tue May 31 2016 - 09:12:27 EST

Hi Robin

During some of the stress tests we also came across a different warning from the arm64 page management code
It looks like a race is detected between HW and SW marking a bit in the PTE

Not sure it's really related but I thought it might give a clue on the issue



> -----Original Message-----
> From: Marcin Wojtas [mailto:mw@xxxxxxxxxxxx]
> Sent: Tuesday, May 31, 2016 13:30
> To: Robin Murphy
> Cc: linux-mm@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-arm-
> kernel@xxxxxxxxxxxxxxxxxxx; Lior Amsalem; Thomas Petazzoni; Yehuda
> Yitschak; Catalin Marinas; Arnd Bergmann; Grzegorz Jaszczyk; Will Deacon;
> Nadav Haklai; Tomasz Nowicki; Gregory ClÃment
> Subject: Re: [BUG] Page allocation failures with newest kernels
> Hi Robin,
> >
> > I remember there were some issues around 4.2 with the revision of the
> > arm64 atomic implementations affecting the cmpxchg_double() in SLUB,
> > but those should all be fixed (and the symptoms tended to be
> considerably more fatal).
> > A stronger candidate would be 97303480753e (which landed in 4.4),
> > which has various knock-on effects on the layout of SLUB internals -
> > does fiddling with L1_CACHE_SHIFT make any difference?
> >
> I'll check the commits, thanks. I forgot to add L1_CACHE_SHIFT was my first
> suspect - I had spent a long time debugging network controller, which
> stopped working because of this change - L1_CACHE_BYTES (and hence
> NET_SKB_PAD) not fitting HW constraints. Anyway reverting it didn't help at
> all for page alloc issue.
> Best regards,
> Marcin