Re: [RFC PATCH 34/37] mm: rcu safe vma freeing only for multithreaded user space

2021-04-08 Thread Michel Lespinasse
On Wed, Apr 07, 2021 at 03:50:06AM +0100, Matthew Wilcox wrote: > On Tue, Apr 06, 2021 at 06:44:59PM -0700, Michel Lespinasse wrote: > > Performance tuning: as single threaded userspace does not use > > speculative page faults, it does not require rcu safe vma freeing. > > Turn this off to avoid th

Re: [RFC PATCH 34/37] mm: rcu safe vma freeing only for multithreaded user space

2021-04-06 Thread Matthew Wilcox
On Tue, Apr 06, 2021 at 06:44:59PM -0700, Michel Lespinasse wrote: > Performance tuning: as single threaded userspace does not use > speculative page faults, it does not require rcu safe vma freeing. > Turn this off to avoid the related (small) extra overheads. > > For multi threaded userspace, we

[RFC PATCH 34/37] mm: rcu safe vma freeing only for multithreaded user space

2021-04-06 Thread Michel Lespinasse
Performance tuning: as single threaded userspace does not use speculative page faults, it does not require rcu safe vma freeing. Turn this off to avoid the related (small) extra overheads. For multi threaded userspace, we often see a performance benefit from the rcu safe vma freeing - even in test