On 19 September 2018 at 17:19, Alex Bennée <alex.ben...@linaro.org> wrote: >> An additional improvement that I have thought of is to get rid >> of memset(-1) altogether. Instead, we'd store addresses in the TLB >> as $real_address+1, so that 0xff..ff is stored as 0x00..00. That way, >> instead of malloc+memset we'd just calloc a new TLB, which >> should be much faster since we'd most likely get zeroed pages >> from mmap. The cost would be an additional instruction in the fast >> path to subtract 1 from the address in the TLB, but this extra >> instruction would be essentially free in modern CPUs. > > Or test for 0 - I'm guessing pretty much any null page access could be > an always slow path as it's likely to be a fault.
Not true for instance for M profile CPUs, where page 0 likely contains the interrupt vector table. thanks -- PMM
