linux-kernel - Re: [BUG] Page allocation failures with newest kernels

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 7 Jun 2016 19:36:57 +0200
From:	Marcin Wojtas <mw@...ihalf.com>
To:	Mel Gorman <mgorman@...hsingularity.net>
Cc:	Will Deacon <will.deacon@....com>,
	Yehuda Yitschak <yehuday@...vell.com>,
	Robin Murphy <robin.murphy@....com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Lior Amsalem <alior@...vell.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Arnd Bergmann <arnd@...db.de>,
	Grzegorz Jaszczyk <jaz@...ihalf.com>,
	Nadav Haklai <nadavh@...vell.com>,
	Tomasz Nowicki <tn@...ihalf.com>,
	Gregory Clément 
	<gregory.clement@...e-electrons.com>
Subject: Re: [BUG] Page allocation failures with newest kernels

Hi Mel,



2016-06-03 14:36 GMT+02:00 Mel Gorman <mgorman@...hsingularity.net>:
> On Fri, Jun 03, 2016 at 01:57:06PM +0200, Marcin Wojtas wrote:
>> >> For the record: the newest kernel I was able to reproduce the dumps
>> >> was v4.6: http://pastebin.com/ekDdACn5. I've just checked v4.7-rc1,
>> >> which comprise a lot (mainly yours) changes in mm, and I'm wondering
>> >> if there may be a spot fix or rather a series of improvements. I'm
>> >> looking forward to your opinion and would be grateful for any advice.
>> >>
>> >
>> > I don't believe we want to reintroduce the reserve to cope with CMA. One
>> > option would be to widen the gap between low and min watermark by the
>> > size of the CMA region. The effect would be to wake kswapd earlier which
>> > matters considering the context of the failing allocation was
>> > GFP_ATOMIC.
>>
>> Of course my intention is not reintroducing anything that's gone
>> forever, but just to find out way to overcome current issues. Do you
>> mean increasing CMA size?
>
> No. There is a gap between the low and min watermarks. At the low point,
> kswapd is woken up and at the min point allocation requests either
> either direct reclaim or fail if they are atomic. What I'm suggesting
> is that you adjust the low watermark and add the size of the CMA area
> to it so that kswapd is woken earlier. The watermarks are calculated in
> __setup_per_zone_wmarks
>

I printed all zones' settings, whose watermarks are configured within
__setup_per_zone_wmarks(). There are three DMA, Normal and Movable -
only first one's watermarks have non-zero values. Increasing DMA min
watermark didn't help. I also played with increasing
/proc/sys/vm/min_free_kbytes from ~2560 to 16000
(__setup_per_zone_wmarks() recalculates watermarks after that) - no
effect either.

Best regards,
Marcin