On 2/27/24 8:26 AM, Vincent Fu wrote: > Starting with gcc 11 __sync_synchronize() compiles to > > lock or QWORD PTR [rsp], 0 > > on x86_64 platforms. Previously it compiled to an mfence instruction. > > See line 47 of https://godbolt.org/z/xfE18K7b4 for an example. > > On Intel platforms this change does not affect the result of fio's CPU > clock test. But on AMD platforms, this change causes fio's CPU clock > test to fail and fio to fall back to clock_gettime() instead of using > the CPU clock for timing. > > This patch has fio explicitly use an mfence instruction instead of > __sync_synchornize() in the CPU clock test code on x86_64 platforms in > order to allow the CPU clock test to pass on AMD platforms. Looks good: Reviewed-by: Jens Axboe <axboe@xxxxxxxxx> -- Jens Axboe
