4 ms·
The performance hit is (supposedly) much more significant on Haswell and older, which they forgot to include.
by teamhappy 9y ago
The performance hit is (supposedly) much more significant on Haswell and older, which they forgot to include.
- hrrsn 9y agoHow convenient.
- deleted 9y ago[deleted]
- hoffs 9y agoI own haswell and haven't felt any performance impact...
- teamhappy 9y ago> For context, on newer CPUs such as on Skylake and > beyond, Intel has refined the instructions used to > disable branch speculation to be more specific to > indirect branches, reducing the overall performance > penalty of the Spectre mitigation. https://cloudblogs.microsoft.com/microsoftsecure/2018/01/09/understanding-the-performance-impact-of-spectre-and-meltdown-mitigations-on-windows-systems/ https://cloudblogs.microsoft.com/microsoftsecure/2018/01/09/...
- dogma1138 9y agoHaswell and Broadwell introduced INVPCID support, unless there were further undocumented improvements I'm not entirely sure what this is based on.
- revelation 9y agoSpecifically, the oldest generation they tested (Skylake) is the first to have the PCID feature that avoids the complete TLB flush on every syscall. Continuing with their strategy of full transparency..
- kogepathic 9y ago> (Skylake) is the first to have the PCID feature PCID was introduced with Westmere (2010). [1] However it wasn't used in the Linux kernel until 4.14 because no one saw the need. [2] [1] https://www.realworldtech.com/westmere/ https://www.realworldtech.com/westmere/ [2] https://stackoverflow.com/questions/20155304/does-linux-use-x86-cpus-pcid-feature-for-tlb-if-not-why https://stackoverflow.com/questions/20155304/does-linux-use-...
- vardump 9y agoBut only Haswell added INVPCID.
- deleted 9y ago[deleted]
- blinkingled 9y agoThis is the key. Without INVPCID PCID is good as useless.