On Tue, 2007-02-13 at 14:45 -0800, Zachary Amsden wrote: > Jeremy Fitzhardinge wrote: > > Add the "nosegneg" fake capabilty to the vsyscall page notes. This is > > used by the runtime linker to select a glibc version which then > > disables negative-offset accesses to the thread-local segment via > > %gs. These accesses require emulation in Xen (because segments are > > truncated to protect the hypervisor address space) and avoiding them > > provides a measurable performance boost. > > > > I don't like this because now a kernel compiled with both CONFIG_XEN and > CONFIG_VMI has "nosegneg" turned on. We don't actually require this for > performance or correctness, so it would be nice to be able to > dynamically turn it off instead of having it forced. Ditto for lguest. Rusty.
