Commits
David Vrabel committed 1c32cdc633c
xen/x86: avoid updating TLS descriptors if they haven't changed When switching tasks in a Xen PV guest, avoid updating the TLS descriptors if they haven't changed. This improves the speed of context switches by almost 10% as much of the time the descriptors are the same or only one is different. The descriptors written into the GDT by Xen are modified from the values passed in the update_descriptor hypercall so we keep shadow copies of the three TLS descriptors to compare against. lmbench3 test Before After Improvement -------------------------------------------- lat_ctx -s 32 24 7.19 6.52 9% lat_pipe 12.56 11.66 7% Signed-off-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>