On Fri, 14 Sep 2018 15:02:07 +0200 Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > On Fri, Sep 14, 2018 at 12:28:24PM +0200, Martin Schwidefsky wrote: > > > I spent some time to get s390 converted to the common mmu_gather code. > > There is one thing I would like to request, namely the ability to > > disable the page gather part of mmu_gather. For my prototype patch > > see below, it defines the negative HAVE_RCU_NO_GATHER_PAGES Kconfig > > symbol that if defined will remove some parts from common code. > > Ugly but good enough for the prototype to convey the idea. > > For the final solution we better use a positive Kconfig symbol and > > add that to all arch Kconfig files except for s390. > > In a private thread ealier Linus raised the point that the batching and > freeing of lots of pages at once is probably better for I$. That would be something to try. For now I would like to do a conversion that more or less preserves the old behavior. You know these pesky TLB related bugs.. > > +config HAVE_RCU_NO_GATHER_PAGES > > + bool > > I have a problem with the name more than anything else; this name > suggests it is the RCU table freeing that should not batch, which is not > the case, you want the regular page gather gone, but very much require > the RCU table gather to batch. > > So I would like to propose calling it: > > config HAVE_MMU_GATHER_NO_GATHER > > Or something along those lines. Imho a positive config option like HAVE_MMU_GATHER_PAGES would make the most sense. It has the downside that it needs to be added to all arch/*/Kconfig files except for s390. But I am not hung-up on a name, whatever does not sound to awful will do for me. HAVE_MMU_GATHER_NO_GATHER would be ok. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin.
