6 ms·
The point is that on PMem that is simply "sfence", and not a potentially super-expensive "fsync" syscall... Fsync is an fsync, not a memory barrier...
by pbalcer 3y ago
The point is that on PMem that is simply "sfence", and not a potentially super-expensive "fsync" syscall... Fsync is an fsync, not a memory barrier...
- adastra22 3y agoThey both involve flushing cache to backing stores, and waiting for confirmation of the write. It’s literally the same thing. It’s just writing a cache line to RAM is orders of magnitude faster than writing a disk sector to storage, even with NVME SSDs. Octane is/was somewhere in the middle.
- Dylan16807 3y ago> They both involve flushing cache to backing stores, and waiting for confirmation of the write. No they don't. A fence only imposes ordering. It's instant. It can increase the chance of a stall when it forbids certain optimizations, but it won't cause a stall by itself. CLWB is a small flush, but as tanelpoder explained the more recent CPUs did not need CLWB.