3 ms·

For Linux 5.0 and as of March this year, the performance impact of enabling Linux kernel mitigations for Spectre/Meltdown against various CPUs with the latest m

by dhx 7y ago

For Linux 5.0 and as of March this year, the performance impact of enabling Linux kernel mitigations for Spectre/Meltdown against various CPUs with the latest microcode (as of March) are: Intel: -13% for the Core i9 7980XE, -17% for the 8086K. AMD: -3% for the 2700X. Reference: https://www.phoronix.com/scan.php?page=article&item=linux50-spectre-meltdown&num=6 https://www.phoronix.com/scan.php?page=article&item=linux50-... Phoronix is due to release new benchmarks tomorrow showing full impact from Spectre/Meltdown/L1TF/MDS. There are some initial benchmarks at https://www.phoronix.com/scan.php?page=news_item&px=MDS-Zombieload-Initial-Impact https://www.phoronix.com/scan.php?page=news_item&px=MDS-Zomb...

adossi 7y ago
What about for the newer processors like the 9980XE, 9900K, etc.? I would have assumed that Intel's latest processors have some additional engineering in place to mitigate the spectre/meltdown performance impacts.
- deleted 7y ago
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- kllrnohj 7y ago
  > What about for the newer processors like the 9980XE The 9980XE is Skylake. It's not actually a "new" processor at all. Consumer parts were released in 2015 (Core ix-6xxx) & server parts in 2015 as well (Xeon E3-v5). In fact the 9980XE itself isn't even a new offering in the HEDT space for Intel, as it's basically a rebrand of the 7980XE. The differences are just a soldered heat-spreader instead of paste & a small clock bump to go along with that. It's +200mhz turbo & +400mhz base, complete with a power consumption increase to match. EDIT: The 9900K (Coffee Lake) does have in-silicon mitigations for Meltdown & L1TF (Foreshadow), though: https://www.anandtech.com/show/13450/intels-new-core-and-xeon-w-processors-fixes-for-spectre-meltdown https://www.anandtech.com/show/13450/intels-new-core-and-xeo...
gnufx 7y ago
Surely the effect depends on what you're running, and you can't put a single number on it. There are actually somewhat contradictory results I've seen for HPC-type applications, and no useful analysis of them with low level profiling.
- ketralnis 7y ago
  For HPC-type applications you're probably not running code from multiple trust domains on one CPU, in which case you might not need the mitigations at all

by dhx 7y ago

adossi 7y ago

What about for the newer processors like the 9980XE, 9900K, etc.? I would have assumed that Intel's latest processors have some additional engineering in place to mitigate the spectre/meltdown performance impacts.

deleted 7y ago
[deleted]
kllrnohj 7y ago
> What about for the newer processors like the 9980XE The 9980XE is Skylake. It's not actually a "new" processor at all. Consumer parts were released in 2015 (Core ix-6xxx) & server parts in 2015 as well (Xeon E3-v5). In fact the 9980XE itself isn't even a new offering in the HEDT space for Intel, as it's basically a rebrand of the 7980XE. The differences are just a soldered heat-spreader instead of paste & a small clock bump to go along with that. It's +200mhz turbo & +400mhz base, complete with a power consumption increase to match. EDIT: The 9900K (Coffee Lake) does have in-silicon mitigations for Meltdown & L1TF (Foreshadow), though: https://www.anandtech.com/show/13450/intels-new-core-and-xeon-w-processors-fixes-for-spectre-meltdown https://www.anandtech.com/show/13450/intels-new-core-and-xeo...

gnufx 7y ago

Surely the effect depends on what you're running, and you can't put a single number on it. There are actually somewhat contradictory results I've seen for HPC-type applications, and no useful analysis of them with low level profiling.

ketralnis 7y ago
For HPC-type applications you're probably not running code from multiple trust domains on one CPU, in which case you might not need the mitigations at all