The Performance Impact To POWER9's Eager L1d Cache Flushing Fix

[AndyChow]

It's not that bad for the fix. This is L1 data flushing, I would have imagined 30%+ problems.

[ms178]

I remember that Michael once did a benchmark shootout between comparable Server-CPUs across all relevant ISA's - a follow-on could be interesting as performance enhancements and new security patches emerged and new CPU generations became available.

[baryluk]

I was expecting the performance drop to be even worse. That is pretty bad, but not catastrophically bad.

Plus many syscall-light workloads are not impacted, as expected.

[CochainComplex]

At least they moved quickly and fixed this very soon.
People bash intel for the security flaws but intel did move quite fast to fix them.
For a server I don't value raw performance as much as I do value security, patches and being a responsible company.

True but in the other Hand x% performance hit means x% less powereficiency. If it is an hpc cluster this is raw money. Vor lets say the otherway around some people in the desktop market want to pay 40%+ to geht the last 5-10% possible.

[ezekrb5]

At least they moved quickly and fixed this very soon.
People bash intel for the security flaws but intel did move quite fast to fix them.
For a server I don't value raw performance as much as I do value security, patches and being a responsible company.

[schmidtbag]

Not the best of news, but it could've been worse.

[phoronix]

Phoronix: The Performance Impact To POWER9's Eager L1d Cache Flushing Fix

Last week a new vulnerability was made public for IBM POWER9 processors resulting in a mitigation of the processor's L1 data cache needing to be flushed between privilege boundaries. Due to the possibility of local users being able to obtain data from the L1 cache improperly when this CVE is paired with other side channels, the Linux kernel for POWER9 hardware is flushing the L1d on entering the kernel and on user accesses. Here are some preliminary benchmarks looking at how this security change impacts the overall system performance.

http://www.phoronix.com/vr.php?view=29731