On Thu 14-12-17 12:42:46, Andrew Morton wrote: > On Thu, 14 Dec 2017 16:17:18 +0100 Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > > as fast as possible, SRCU instead of reference count is used to > > > implement get/put_swap_device(). From get_swap_device() to > > > put_swap_device(), the reader side of SRCU is locked, so > > > synchronize_srcu() in swapoff() will wait until put_swap_device() is > > > called. > > > > It is quite unfortunate to pull SRCU as a dependency to the core kernel. > > Different attempts to do this have failed in the past. This one is > > slightly different though because I would suspect that those tiny > > systems do not configure swap. But who knows, maybe they do. > > > > Anyway, if you are worried about performance then I would expect some > > numbers to back that worry. So why don't simply start with simpler > > ref count based and then optimize it later based on some actual numbers. > > Btw. have you considered pcp refcount framework. I would suspect that > > this would give you close to SRCU performance. > > <squeaky-wheel>Or use stop_kernel() ;)</squeaky-wheel> well, stop_kernel is a _huge_ hammer. I think we can do much better without a large complexity. A simple ref counting (or pcp refcounting if the former has measurable complexity) should do just fine. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
