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Mon Mar 21 21:14:43 UTC 2011


for the file system to take care of and point at things like snapshots 
(e.g. in BTRFS) and deduplication (last time I was involved in a discussion 
on deduping on the BTRFS list I was sufficiently disappointed by the 
wrongness of the proposed designs I just gave up - thankfully, we now have 
a fully working ZFS port for Linux so I never have to look at BTRFS again). 
BTRFS guys neither seemed to comprehend the importance of CoW hard-links 
nor had any interest in implementing such a feature.

Here's the relevant thread on the BTRFS list:
http://www.spinics.net/lists/linux-btrfs/msg05224.html

Given the lack of interest and understanding from both the LXC camp and  
the BTRFS camp, I don't actually see any alternative to the efficiency of 
vserver any time soon. There are other bodge solutions that may be viable, 
such as marking all memory for same-page merging using LD_PRELOAD 
intercepts of malloc(), as I mentioned here:
http://www.spinics.net/lists/kvm/msg36193.html
but that would still be relatively expensive - KSM iterates through and  
dedupes all the madvise()-ed memory every few seconds. In comparison, the 
vserver's hashify feature is free in terms of run-time overheads.

Gordan

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Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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