From f1a042b9829687affabb95c7c1cbcde29f1d36bd Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Thu, 22 Apr 2021 13:26:26 +0200 Subject: [PATCH] x86/time: yield to hyperthreads after updating TSC during rendezvous MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Since we'd like the updates to be done as synchronously as possible, make an attempt at yielding immediately after the TSC write. Signed-off-by: Jan Beulich Reviewed-by: Roger Pau Monné --- xen/arch/x86/time.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c index e92365f5bd..5578b7b3a2 100644 --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -1708,7 +1708,14 @@ static void time_calibration_tsc_rendezvous(void *_r) atomic_inc(&r->semaphore); if ( i == 0 ) + { write_tsc(master_tsc); + /* + * Try to give our hyperthread(s), if any, a chance to do + * the same as instantly as possible. + */ + cpu_relax(); + } while ( atomic_read(&r->semaphore) != (2*total_cpus - 1) ) cpu_relax(); @@ -1730,7 +1737,14 @@ static void time_calibration_tsc_rendezvous(void *_r) } if ( i == 0 ) + { write_tsc(master_tsc); + /* + * Try to give our hyperthread(s), if any, a chance to do + * the same as instantly as possible. + */ + cpu_relax(); + } atomic_inc(&r->semaphore); while ( atomic_read(&r->semaphore) > total_cpus ) -- 2.30.2