On Wed, Aug 10, 2022 at 10:31:56PM -0400, Joel Fernandes wrote: > > > On 8/10/2022 10:23 PM, Joel Fernandes wrote: > > > > > > On 8/8/2022 11:45 PM, Joel Fernandes (Google) wrote: > >> Just a refresh of v3 with one additional debug patch. v3's cover letter is here: > >> https://lore.kernel.org/all/20220713213237.1596225-1-joel@xxxxxxxxxxxxxxxxx/ > >> > >> I just started working on this again while I have some time during paternity > >> leave ;-) So I thought I'll just send it out again. No other changes other > >> than that 1 debug patch I added on the top. > >> > >> Next I am going to go refine the power results as mentioned in Paul's comments > >> on the last cover letter. > > > > Side note: Here is another big selling point for call_rcu_lazy(). > > Instead of _lazy(), if you just increased jiffies_till_first_fqs, and > > slowed *all* call_rcu() down to achieve the same effect, that would > > affect percpu refcounters switching to atomic-mode, for example. > > > > They switch to atomic mode by calling __percpu_ref_switch_mode() which > > is called by percpu_ref_switch_to_atomic_sync().> > > This will slow this call down for the full lazy duration which will slow > > down suspend in blk_pre_runtime_suspend(). > > Correction while I am going on the record (got to be careful these > days). It *might* slow down RCU for the full lazy duration, unless of > course a fly-by rescue call_rcu() comes in. Just unload a module, which if I remember correctly invokes rcu_barrier(). Lots of rescue callbacks. ;-) Thanx, Paul
