Re: memcg: cat: memory.memsw.* : Operation not supported

[Kamezawa Hiroyuki]

(2012/06/28 5:24), Tejun Heo wrote:
> Hello,
>
> On Wed, Jun 27, 2012 at 01:21:27PM -0700, David Rientjes wrote:
> > Well it also has a prerequisite that memcg doesn't have: CONFIG_SWAP, so
>
> Right.
>
> > even if CONFIG_CGROUP_MEM_RES_CTLR_SWAP is folded into
> > CONFIG_CGROUP_MEM_RES_CTLR, then these should still depend on CONFIG_SWAP
> > since configuring them would imply there is some limit to be enforced.
> >
> > But to answer your question:
> >
> >     text	   data	    bss	    dec	    hex	filename
> >    25777	   3644	   4128	  33549	   830d	memcontrol.o.swap_disabled
> >    27294	   4476	   4128	  35898	   8c3a	memcontrol.o.swap_enabled
>
> I still wish it's folded into CONFIG_MEMCG and conditionalized just on
> CONFIG_SWAP tho.

In old days, memsw controller was not very stable. So, we devided the config.
And, it makes size of memory for swap-device double (adds 2bytes per swapent.)
That is the problem.

> > Is it really too painful to not create these files when
> > CONFIG_CGROUP_MEM_RES_CTLR_SWAP is disabled?  If so, can we at least allow
> > them to be opened but return -EINVAL if memory.memsw.limit_in_bytes is
> > written?
>
> Not at all, that was the first version anyway, which (IIRC) KAME
> didn't like and suggested always creating those files.  KAME, what do
> you think?

IIRC...at that time, we made decision, cgroup has no feature to
'create files dynamically'. Then, we made it in static, decision was done
at compile time and ignores "do_swap_account".

Now, IIUC, we have the feature. So, it's may be a time to create the file
with regard to "do_swap_account", making decision at boot time.


Thanks,
-Kame



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