Re: [PATCH for 3.2.34] memcg: do not trigger OOM fromadd_to_page_cache_locked

[Michal Hocko]

On Tue 05-02-13 15:49:47, azurIt wrote:
[...]
> I have another old problem which is maybe also related to this. I
> wasn't connecting it with this before but now i'm not sure. Two of our
> servers, which are affected by this cgroup problem, are also randomly
> freezing completely (few times per month). These are the symptoms:
>  - servers are answering to ping
>  - it is possible to connect via SSH but connection is freezed after
>  sending the password
>  - it is possible to login via console but it is freezed after typeing
>  the login
> These symptoms are very similar to HDD problems or HDD overload (but
> there is no overload for sure). The only way to fix it is, probably,
> hard rebooting the server (didn't find any other way). What do you
> think? Can this be related?

This is hard to tell without further information.

> Maybe HDDs are locked in the similar way the cgroups are - we already
> found out that cgroup freezeing is related also to HDD activity. Maybe
> there is a little chance that the whole HDD subsystem ends in
> deadlock?

"HDD subsystem" whatever that means cannot be blocked by memcg being
stuck. Certain access to soem files might be an issue because those
could have locks held but I do not see other relations.

I would start by checking the HW, trying to focus on reducing elements
that could contribute - aka try to nail down to the minimum set which
reproduces the issue. I cannot help you much with that I am afraid.
-- 
Michal Hocko
SUSE Labs
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