feasibility of modifying Linux ld-linux.so to identify which mappedfiles are shared libraries

[Ray Bryant <raybry at engr dot sgi dot com>]

I've been working on a project referred to as "manual page migration" for 
Linux.  (Please bear with me, relevance to this list will be established
asap...)  Briefly, the purpose of this project is to allow a batch manager
on a large NUMA system to move pages of an application from one set of
NUMA nodes to another.  Obviously, we just want to move application pages,
and shared libraries (and shared, read-only data segments) should not be
moved.  To do this, we need a reliable, configurable way to mark such files
as to whether or not they should be moved.

To date, we have been using an extended attribute "system.migration" to
mark mapped files as either migratable (the default), a library, or
not-migratable.  (This extended attribute requires a file-system patch to
the kernel to support.)  In the library case, we move anonymous pages
(this is presumably process specific data) but not shared pages.

Christoph Hellwig has suggested that instead we modify the dynamic loader
to mark mapped files in kernel memory as being shared libraries; this would
likely be communicated to the kernel via a new MMAP flag.

So (finally, here is the question for this mailing list:)  "Would a
patch for ld-linux.that added such marking so be considered by the glibc
developers, or would such an approach be rejected?"  Alternatively, "Is
such a patch clearly infeasible for technical reasons?"

(Obviously, I don't want to pursue this approach, if, from the start,
it is doomed.  :-) )

Further details of this project and discussion can be found at:

http://marc.theaimsgroup.com/?l=linux-mm&m=111276123522952&w=2

and the more recent discussion is at:

http://marc.theaimsgroup.com/?l=linux-mm&m=111578651020174&w=2

--
Best Regards,
Ray
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                  Ray Bryant
512-453-9679 (work)         512-507-7807 (cell)
raybry@sgi.com             raybry@austin.rr.com
The box said: "Requires Windows 98 or better",
           so I installed Linux.
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