On Mon, Feb 10, 2014 at 02:15:14PM +0100, Josep Lladonosa wrote:

On 10 February 2014 12:40, Gabriel de Perthuis [off-list ref] wrote:

quoted

quoted

Hello,

I am using bcache in my laptop (RAM 32 GiB). I have been using it
perfectly for a month. ext4 + bcache.

Yesterday, system did not want do to a normal startup. Messages where
from udev out of memory (and udevadm killed?) and system was not
mounting / (/dev/bcache0).

[    6.823222] bcache-register invoked oom-killer: gfp_mask=0x82d2,
order=0, oom_score_adj=0

Build your kernel with CONFIG_COMPACTION.  I've added it to the FAQ:
http://bcache.evilpiepirate.org/~kent/bcache/FAQ/

Hello Gabriel,

Thanks for your reply.

My .config file has already:
...
CONFIG_COMPACTION=y

I looked at the allocations done in bcache_device_init(), those aren't high
order page allocations (they're vmalloc allocations) so compaction won't help
here.

...

I have been digging around to find information and sometimes bugs come
related to unsigned variables and their operations when storing large
numbers (reserved memory?). Kernel is 64 bits. Memory is 32 GiB.
Perhaps it could happen that the allocated memory is not totally
freed.

When kernel has been able to boot with 32 GiB (having bcache0 messed
up and bcache1 mountable), it seems that bcache has more than 16 GiB
allocated and kept.

Woah, really? If so that's bad - I don't see how that follows (or am I
misreading) from your numbers, can you show a before and after when you bring
bcache up?

-Free memory with kernel 3.11.0-rc7 with 32GiB and bcache0 (halved?)
and bcache1 (mounted)

$ head -2 /proc/meminfo
MemTotal:       32913872 kB
MemFree:        12376640 kB


- Free memory with kernel 3.12.9 with mem=16G and bcache0 (mounted)

$ head -2 /proc/meminfo
MemTotal:       15602144 kB
MemFree:        14005372 kB

quoted

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Salutacions...Josep
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