On 21/03/24(Thu) 13:36, Mateusz Guzik wrote:
> On Thu, Mar 21, 2024 at 1:22 PM Alexander Bluhm <alexander.bluhm@gmx.net> wrote:
> [..] 
> I also got about 5% in terms of system time.
> 
> I'm not going to argue about the style, but I'm going to note some
> extra stuff. :)

Thanks for the notes.  It's always interesting to have suggestions.  

> 2 speed ups on top of this would come from:
> 1. reducing lock access in mtx_enter_try to begin with. most notably
> IPL level could be read off only once, not every single time
> execuction lands there
> 2. backoff could be added, even something as simple as exponentially
> going to up to 8 spins would be an improvement with more cpus
> 
> however, vast majority of the win is already there with the initial patch
> 
> That aside I think there is an avoidable overcounting of spinning --
> even the initial attempt at taking the lock is enclosed by
> spc_spinning. I would suggest prefixing the code with a mere
> mtx_enter_try. Should that fail, drop down to a do { } while loop
> which spins first and tries to lock later.

Please submit a tested diff.  Without offence, talk is cheap and we are
all already busy with others priorities.  However diffs are more than
welcome.

Thanks.