Re: [4.7.0rc6] Page Allocation Failures with dm-crypt

From: Mike Snitzer
Date: Mon Jul 11 2016 - 09:45:00 EST

On Mon, Jul 11 2016 at 9:27am -0400,
Matthias Dahl <ml_linux-kernel@xxxxxxxxxxxxxxxx> wrote:

> Hello Mike...
> On 2016-07-11 15:18, Mike Snitzer wrote:
> >Something must explain the execessive nature of your leak but
> >it isn't a known issue.
> Since I am currently setting up the new machine, all tests were
> performed w/ various live cd images (Fedora Rawhide, Gentoo, ...)
> and I saw the exact same behavior everywhere.
> >Have you tried running with kmemleak enabled?
> I would have to check if that is enabled on the live images but even if
> it is, how would that work? The default interval is 10min. If I fire up
> a dd, the memory is full within two seconds or so... and after that, the
> OOM killer kicks in and all hell breaks loose unfortunately.

You can control when kmemleak scans. See Documentation/kmemleak.txt

You could manually trigger a scan just after the dd is started.

But I doubt the livecds have kmemleak compiled into their kernels.

> I don't think this is a particular unique issue on my side. You could,
> if I am right, easily try a Fedora Rawhide image and reproduce it there
> yourself. The only unique point here is my RAID10 which is a Intel Rapid
> Storage s/w RAID. I have no clue if this could indeed cause such a "bug"
> and how.

What is your raid10's full stripesize? Is your dd IO size of 512K
somehow triggering excess R-M-W cycles which is exacerbating the