On 08/07/2016 22:24, Sergey Fedorov wrote: > I remember, I've just found that we discussed it in this thread: > > http://thread.gmane.org/gmane.comp.emulators.qemu/401723/focus=406852 > > I was thinking of just doing 'tb_jmp_cache' lookup out of the lock, not > tb_find_physical(). Now thanks to QHT, we could do tb_find_physical() > out of the lock, too. This changes things.
But in my patch ("tcg: move tb_find_fast outside the tb_lock critical section", which originally was written by Fred---most of my contribution was getting the invalidation right, not the lock-free lookup) tb_find_physical was also done out of the lock. It was then retried inside the lock, if it failed. This is why I needed to fail all concurrent lookups as the first step in the invalidation. Emilio's QHT resulted in a rewrite of tb_find_physical, but the basic concepts are the same. Paolo