3 ms·
Strictly speaking, the sentence "I/O is faster then CPU", aka "memory access is faster then computations" is nonsense, because it compares apples with bananas.
by ktpsns 8y ago
Strictly speaking, the sentence "I/O is faster then CPU", aka "memory access is faster then computations" is nonsense, because it compares apples with bananas. One could probably say "transfering x data between CPU and SSD is faster then performing the computation f(x) on the CPU", where still f remains undefined.
- deleted 8y ago[deleted]
- otterley 8y agoThe issue being discussed in the article and amongst OS designers is that I/O throughput volumes being seen in the wild today are unable to be accepted in real time (i.e., without significant queueing delays) by otherwise unloaded CPUs.
- masklinn 8y agoYou're misreading the article. Its subject is that because of the way IO stacks have been built CPUs are becoming the bottleneck in IO, this is an issue for both network and non-volatile storage IO e.g. > a 40 GbE NIC can receive a cache line sized packet every 5 ns, but the last level cache (LLC) access latency is already up to 15 ns, which means a single LLC access can already prevent the OS from keeping up with arriving packets and > NVMe SSDs perform I/O faster than the OS can accept new (asynchronous) I/O requests and notify their completion. They also note e.g. that while nvme provides for 65k command queues OS generally have one IO queue per CPU.
- jeanmichelx 8y agoLatency ≠ throughput