> From: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> > Sent: Tuesday, March 21, 2023 6:28 PM > [...] > Subject: [PATCH 1/1] Reduce synchronize_rcu() waiting time > > A call to a synchronize_rcu() can be expensive from time point of view. > Different workloads can be affected by this especially the ones which use this > API in its time critical sections. > This is interesting and meaningful research. ;-) > For example in case of NOCB scenario the wakeme_after_rcu() callback > invocation depends on where in a nocb-list it is located. Below is an example > when it was the last out of ~3600 callbacks: > > <snip> > <...>-29 [001] d..1. 21950.145313: rcu_batch_start: rcu_preempt > CBs=3613 bl=28 > ... > <...>-29 [001] ..... 21950.152578: rcu_invoke_callback: rcu_preempt > rhp=00000000b2d6dee8 func=__free_vm_area_struct.cfi_jt > <...>-29 [001] ..... 21950.152579: rcu_invoke_callback: rcu_preempt > rhp=00000000a446f607 func=__free_vm_area_struct.cfi_jt > <...>-29 [001] ..... 21950.152580: rcu_invoke_callback: rcu_preempt > rhp=00000000a5cab03b func=__free_vm_area_struct.cfi_jt > <...>-29 [001] ..... 21950.152581: rcu_invoke_callback: rcu_preempt > rhp=0000000013b7e5ee func=__free_vm_area_struct.cfi_jt > <...>-29 [001] ..... 21950.152582: rcu_invoke_callback: rcu_preempt > rhp=000000000a8ca6f9 func=__free_vm_area_struct.cfi_jt > <...>-29 [001] ..... 21950.152583: rcu_invoke_callback: rcu_preempt > rhp=000000008f162ca8 func=wakeme_after_rcu.cfi_jt > <...>-29 [001] d..1. 21950.152625: rcu_batch_end: rcu_preempt CBs- > invoked=3612 idle=.... > <snip> > Did the results above tell us that CBs-invoked=3612 during the time 21950.145313 ~ 21950.152625? If possible, may I know the steps, commands, and related parameters to produce the results above? Thank you! - Qiuxu > As performance results, i will provide it once we are ready with a patch. > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> > --- > kernel/rcu/tree.c | 104 > +++++++++++++++++++++++++++++++++++++++++++++- [...]
