[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] copy on write memory



> >
> > Is there any documentation on the semantics of DCSS and the hypervisor
> > services that are used? It would be interesting to see if Xen ought to
> > have some similar concept.
> 
> This doesn't really answer your question - but the closest your likely
> to get is at their pubs:
> 
> http://www.vm.ibm.com/pubs/

There's a manual called "How to Improve the Performance of Linux on
z/VM with Execute-In-Place Technology", which is easily googled for.
Turns out that DCSSs are pretty simple things -- just a blob of
physmem that is mapped into phys address space of every Linux
instance, and contains a read-only filesystem image. xip2fs is a
simple read-only fs that serves mmap() requests directly out of the
shared DCSS rather than the private block cache. Looks tedious to
manage because the whole filesystem takes up space in every Linux
memory map all the time, no matter whether a particular file/block is
being used. So you have to be careful to put only frequently accessed
and highly shared files in the filesystem and use twisted symlinks to
link in from their usual location into the mounted xip2fs filesystem. 

 -- Keir


-------------------------------------------------------
This SF.Net email is sponsored by: InterSystems CACHE
FREE OODBMS DOWNLOAD - A multidimensional database that combines
robust object and relational technologies, making it a perfect match
for Java, C++,COM, XML, ODBC and JDBC. www.intersystems.com/match8
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.sourceforge.net/lists/listinfo/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.