Messages in this thread | | | Subject | Re: [Xen-devel] [patch 17/44] Add nosegneg capability to the vsyscall page notes | From | Rusty Russell <> | Date | Tue, 17 Jul 2007 10:45:55 +1000 |
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On Mon, 2007-07-16 at 16:15 -0700, Jeremy Fitzhardinge wrote: > plain text document attachment (xen-vsyscall-note.patch) > 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.
Hmm, this is still unconditional? Not that it causes any measurable slowdown when enabled, but ISTR discussing making this dynamic...
Rusty.
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