Re: [vserver] Unification and memory usage

From: Herbert Poetzl <>
Date: Tue 03 May 2011 - 00:21:01 BST
Message-ID: <>

On Mon, May 02, 2011 at 11:20:30PM +0100, Gordan Bobic wrote:

> On 02/05/2011 23:14, Roderick A. Anderson wrote:
>> I've got myself confused again. Could someone confirm or deny
>> how unification affects memory usage.

>> I was under the impression that if a unified (hard linked)
>> "program" was started by one guest the code for it went into
>> the text area of memory and any needed data area was allocated
>> from the heap. Then when another guest started the same
>> program kernel-magic happened and basically the same code was
>> used but a new chunk of heap was allocated/used for its data.

>> I'd like to make a simplified drawing of how the Linux-Vserver
>> way with unification saves memory. Have I got it all wrong?

> I believe the memory unification only applies to the shared
> memory mmap-ed from hard-linked DLLs. If you have the same
> glibc unified across all your guests, only one instance of it
> will be in memory. Unified executables won't save you memory in
> this way.

why not?

> What you will gain on all unified files, however, is caching
> efficiency, as you won't end up with multiple copies of the
> same file being cached separately.

so why should the read only mappings (code)
not be shared when executing the _same_
binary twice?


> Gordan
Received on Tue May 3 00:21:12 2011

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