Re: echo dev > /sys/fs/bcache/register gives page allocation failure: order:4, mode:0x2040d0

[Marc MERLIN <marc@merlins.org>]

On Mon, Feb 15, 2016 at 01:02:55PM +0100, Johannes Thumshirn wrote:
> > So I did
> > make-bcache -B /dev/md5
> > echo /dev/md5 > /sys/fs/bcache/register
> > 
> > and it fails:
> > bash: page allocation failure: order:4, mode:0x2040d0
> 
> Is this system under some kind of memory preassure? Did this happen right
> after boot or when the system was already running for quite some time?
 
Uptime 17 days, it's a server that does a lot of I/O, but free shows I have
6GB available for buffer cache out of 8, so that shouldn't be too bad. Seems
like I'm hitting an issue with memory fragmentation or a specific kind of
memory not being available?
(but I don't have any other kernel processes complaining about memory
allocation failure, at least not consistently like here)

On Mon, Feb 15, 2016 at 03:11:04AM -0900, Kent Overstreet wrote:
> > and it fails:
> > bash: page allocation failure: order:4, mode:0x2040d0
> 
> You want CONFIG_COMPACTION=y

Good suggestion, but I already have it:
gargamel:~# grep CONFIG_COMPACTION /boot/config-4.3.3-amd64-i915-volpreempt-20150421
CONFIG_COMPACTION=y

Thanks for the replies,
Marc
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