On Wed, Aug 24, 2022 at 8:14 PM Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > > On Wed, Aug 24, 2022 at 12:59 PM Kumar Kartikeya Dwivedi > <memxor@xxxxxxxxx> wrote: > > > > On Fri, 19 Aug 2022 at 23:43, Alexei Starovoitov > > <alexei.starovoitov@xxxxxxxxx> wrote: > > > > > > From: Alexei Starovoitov <ast@xxxxxxxxxx> > > > > > > SLAB_TYPESAFE_BY_RCU makes kmem_caches non mergeable and slows down > > > kmem_cache_destroy. All bpf_mem_cache are safe to share across different maps > > > and programs. Convert SLAB_TYPESAFE_BY_RCU to batched call_rcu. This change > > > solves the memory consumption issue, avoids kmem_cache_destroy latency and > > > keeps bpf hash map performance the same. > > > > > > Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> > > > > Makes sense, there was a call_rcu_lazy work from Joel (CCed) on doing > > this batching using a timer + max batch count instead, I wonder if > > that fits our use case and could be useful in the future when it is > > merged? > > > > https://lore.kernel.org/rcu/20220713213237.1596225-2-joel@xxxxxxxxxxxxxxxxx > > Thanks for the pointer. It looks orthogonal. > timer based call_rcu is for power savings. > I'm not sure how it would help here. Probably wouldn't hurt. > But explicit waiting_for_gp list is necessary here, > because two later patches (sleepable support and per-cpu rcu-safe > freeing) are relying on this patch. Hello Kumar and Alexei, Kumar thanks for the CC. I am seeing this BPF work for the first time so have not gone over it too much - but in case the waiting is synchronous by any chance, call_rcu_lazy() could hurt. The idea is to only queue callbacks that are not all that important to the system while keeping it quiet (power being the primary reason but Daniel Bristot would concur it brings down OS noise and helps RT as well). Have a good evening, Thank you, - Joel
