OpenVZ Forum


Home » Mailing lists » Devel » [PATCH v3 04/13] kmem accounting basic infrastructure
Re: [PATCH v3 04/13] kmem accounting basic infrastructure [message #48073 is a reply to message #48072] Wed, 26 September 2012 20:02 Go to previous messageGo to previous message
Glauber Costa is currently offline  Glauber Costa
Messages: 916
Registered: October 2011
Senior Member
On 09/26/2012 11:56 PM, Tejun Heo wrote:
> Hello,
>
> On Wed, Sep 26, 2012 at 11:46:37PM +0400, Glauber Costa wrote:
>> Besides not being part of cgroup core, and respecting very much both
>> cgroups' and basic sanity properties, kmem is an actual feature that
>> some people want, and some people don't. There is no reason to believe
>> that applications that want will live in the same environment with ones
>> that don't want.
>
> I don't know. It definitely is less crazy than .use_hierarchy but I
> wouldn't say it's an inherently different thing. I mean, what does it
> even mean to have u+k limit on one subtree and not on another branch?
> And we worry about things like what if parent doesn't enable it but
> its chlidren do.
>

It is inherently different. To begin with, it actually contemplates two
use cases. It is not a work around.

The meaning is also very well defined. The meaning of having this
enabled in one subtree and not in other is: Subtree A wants to track
kernel memory. Subtree B does not. It's that, and never more than that.
There is no maybes and no buts, no magic knobs that makes it behave in a
crazy way.

If a children enables it but the parent does not, this does what every
tree does: enable it from that point downwards.

> This is a feature which adds complexity. If the feature is necessary
> and justified, sure. If not, let's please not and let's err on the
> side of conservativeness. We can always add it later but the other
> direction is much harder.
>

I disagree. Having kmem tracking adds complexity. Having to cope with
the use case where we turn it on dynamically to cope with the "user page
only" use case adds complexity. But I see no significant complexity
being added by having it per subtree. Really.

You have the use_hierarchy fiasco in mind, and I do understand that you
are raising the flag and all that.

But think in terms of functionality: This thing here is a lot more
similar to swap than use_hierarchy. Would you argue that memsw should be
per-root ?

The reason why it shouldn't: Some people want to limit memory
consumption all the way to the swap, some people don't. Same with kmem.
 
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Previous Topic: [PATCH v3 00/16] slab accounting for memcg
Next Topic: [RFC PATCH 0/5] net: socket bind to file descriptor introduced
Goto Forum:
  


Current Time: Sun Aug 31 08:09:02 GMT 2025

Total time taken to generate the page: 0.08046 seconds