On Wed, Mar 2, 2022 at 10:12 AM David Laight <David.Laight@xxxxxxxxxx> wrote: > > > > Atomic operations aren't magic. > > > Atomic operations are (at best) one slow locked bus cycle. > > > Acquiring a lock is the same. > > > Releasing a lock might be cheaper, but is probably a locked bus cycle. > > > > > > So if you use state_lock to protect pages_nr then you lose an atomic > > > operation for the decrement and gain one (for the unlock) in the increment. > > > That is even or maybe a slight gain. > > > OTOH a 64bit atomic is a PITA on some 32bit systems. > > > (In fact any atomic is a PITA on sparc32.) > > > > It's actually *stale_lock* and it's very misleading to use it for this. > > I would actually like to keep atomics but I have no problem with > > making it 32-bit for 32-bit systems. Would that work for you guys? > > It would be better to rename the lock. No it would not because that lock is protecting the list of entries that could not be immediately freed. ~Vitaly
