Hello, Vishalc! > Hi Uladzislau, > > On 12/01/26 15:38, Uladzislau Rezki wrote: > > On Mon, Jan 12, 2026 at 03:13:33PM +0530, Vishal Chourasia wrote: > > > Performance data on a PPC64 system with 400 CPUs: > > > > > > + ppc64_cpu --smt=1 (SMT8 to SMT1) > > > Before: real 1m14.792s > > > After: real 0m03.205s # ~23x improvement > > > > > > + ppc64_cpu --smt=8 (SMT1 to SMT8) > > > Before: real 2m27.695s > > > After: real 0m02.510s # ~58x improvement > > > > > > Above numbers were collected on Linux 6.19.0-rc4-00310-g755bc1335e3b > > > > > > [1] > > > https://lore.kernel.org/all/5f2ab8a44d685701fe36cdaa8042a1aef215d10d.ca...@linux.vnet.ibm.com > > > > > Also you can try: echo 1 > > > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp > > to speedup regular synchronize_rcu() call. But i am not saying that it > > would beat > > your "expedited switch" improvement. > > # echo 1 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp > > After setting, > > # time ppc64_cpu --smt=1; > real 1m10.726s # Run 1 > real 1m12.530s # Run 2 > > # time ppc64_cpu --smt=8 > real 0m36.661s # Run 1 > real 0m41.401s # Run 2 > Thanks.
"ppc64_cpu --smt=1" is the same, i assume it is offlining. "ppc64_cpu --smt=8", whereas, onlining, sees the differences(~5x). But your real "0m02.510s" is hard to beat event by activating the "rcu_normal_wake_from_gp" option. -- Uladzislau Rezki
