Performance Benchmark for PTI (aka Meltdown mitigation)

[Ed Maste]

On 9 March 2018 at 07:01, Slawa Olhovchenkov <slw at zxy.spb.ru> wrote:
> On Thu, Mar 08, 2018 at 05:04:11PM -0500, Arshan Khanifar wrote:
>
>> Executive Summary:
>> - The PTI feature increases the system call times by more than 100%.
>> - As a macrobenchmark, buildworld was used. Wall clock and user time
>> showed no statistically-significant changes, while system time
>> increased by less than 5%.
>>
>> This email contains the results for benchmarking the performance of the
>> PTI patch on FreeBSD 12-current. As a microbenchmark, timing of
>> getppid(2) system call was used, and as a macrobenchmark, a number of
>> buildworld tasks were timed.
>>
>
> Can you also run pre-patched kernel?

It's not easy to do an apples-to-apples comparison as there were a few
followup changes to the PTI work, interspersed with unrelated changes.
That said, I think Arshan has some benchmarks obtained during the
development of the PTI changes that may be illustrative.

The best approach is probably to compare stable/11 at r329450 (last
stable/11 revision before the merge) with r329462 with PTI and IBRS
disabled.