Thread time! Why can't they just quickly patch #meltdown or #spectre and push out another cpu? Why could it possibly take years? Why don't they use AGILE or x/y/z? Lots of reasons:
(note: my goal is not to criticize chip manufacturers - it's to defend the constraints they have)
Yes, it'd likely be like the P4 disaster with deep pipelines constantly getting flushed.
-
-
But maybe not as bad. Modern Intel chips are nowhere near as bad as P4 under fully unpredictable load (effectively random branches).
-
So a typical hit of "only" 30% might be realistic.
-
I like the optimism, but we've got decades of compilers optimizing to hint speculative execution instead of optimizing the code itself. It'd be nowhere as bad as P4 since the pipeline is shorter, but you're talking about a full stall, flush, & waiting for _every_single_branch_
-
Execution stall, yes, but decode/pipeline-fill can still happen speculatively. No idea if the chip has a way to disable execution w/o disabling decode/fill tho.
-
Wouldn’t an execution stall with hyper threading still hide a new TLB miss? For example, speculative execution isn’t that much help if you’re stalled anyways. So increasing the miss rate may not affect the performance that dramatically in that case.
-
Whereas if I wrote “perfect” code with no stalls, the instruction fetch would be dramatically more noticeable, and this is what scares me. Network hardware, system level processes, etc... are usually optimized this way and they are the most critical.
-
These processes slowing down by even 10% is an internet level outage in the making.
-
The latency would propagate exponentially throughout the internet going up the levels of abstraction. Higher dns latency, slower tls/crypto, drop in throughout, then the latency of high-level services would increase by an order of magnitude, then the applications depending on it
- 4 more replies
New conversation -
Loading seems to be taking a while.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.