Re: [ckrm-tech] [PATCH] BC: resource beancounters (v4) (added user memory)

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Pavel Emelianov wrote:

Kirill Korotaev wrote:

[snip]

I have a C program that computes limits to obtain desired guarantees
in a single 'for (i = 0; i < n; n++)' loop for any given set of guarantees.
With all error handling, beautifull output, nice formatting etc it weights
only 60 lines.


Look at http://wiki.openvz.org/Containers/Guarantees_for_resources
I've described there how a guarantee can be get with limiting in details.

[snip]


I do not 'do not like guarantee'. I'm just sure that there are two ways
for providing guarantee (for unreclaimable resorces):
1. reserving resource for group in advance
2. limit resource for others
Reserving is worse as it is essentially limiting (you cut off 100Mb from
1Gb RAM thus limiting the other groups by 900Mb RAM), but this limiting
is too strict - you _have_ to reserve less than RAM size. Limiting in
run-time is more flexible (you may create an overcommited BC if you
want to) and leads to the same result - guarantee.

I think this deserves putting on Wiki.
It is very good clear point.


This is also on the page I gave link at.



This approach has the following disadvantages
 1. Lets consider initialization - When we create 'n' groups initially, we need
    to spend O(n^2) time to assign guarantees.
 2. Every time a limit or a guarantee changes, we need to recalculate guarantees
    and ensure that the change will not break any guarantees
 3. The same thing as stated above, when a resource group is created or deleted

This can lead to some instability; a change in one group propagates to all other groups.


--

	Balbir Singh,
	Linux Technology Center,
	IBM Software Labs
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