[Pkg-xen-devel] Xen and glibc

Julien Danjou acid at debian.org
Wed Mar 15 16:38:37 UTC 2006


We [the Debian Xen package team] are currently working on Xen packages,
and are planning to include them into Debian.

A current issue in Xen, is the libc problem.

From the Xen wiki [1]:
"Xen uses segmentation to provide protection of the memory used for the
hypervisor. This results in some performance issues since wrap-around
segments as used by glibc need expensive extra handling. [...]

It is possible to rebuild glibc so that it only uses segments such that
there is no performance penalty. To do this, you need to apply the patch
below to the glibc sources and then rebuild glibc with the
-mno-tls-direct-seg-refs option."

Currently, we expect our users to move /lib/tls away (or to create
/etc/ld.so.hwnocap, thanks to aurel32 for the tips).
You will understand that this is not very convenient, and will disable
more stuff than really needed.

Would it possible to add an extra flavor to the current glibc with the
correct build options ?

Please note that this issue is only available for i386 arch.

[1] http://wiki.xensource.com/xenwiki/XenSpecificGlibc

Julien Danjou
.''`.  Debian Developer
: :' : http://julien.danjou.info
`. `'  http://people.debian.org/~acid
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