Meltdown and Spectre patches have a variable impact and can cause unwanted reboots, Intel warns

Intel has published the results of the test conducted on the Meltdown and Spectre patches and their impact on performance confirming serious problems.

According to the tech giant systems with several types of processors running Meltdown and Spectre patches may experience more frequent reboots.

A few days ago Intel reported that extensive test conducted on home and business PCs demonstrated a negligible performance impact on these types of systems (from 2 up to 14%).

Now the vendor has conducted some performance tests on data centers and results show that the impact on the performance depends on the system configuration and the workload.

“As expected, our testing results to date show performance impact that ranges depending on specific workloads and configurations. Generally speaking, the workloads that incorporate a larger number of user/kernel privilege changes and spend a significant amount of time in privileged mode will be more adversely impacted.” reads the analysis conducted by Intel.

Impacts ranging from 0-2% on industry-standard measures of integer and floating point throughput, Linpack, STREAM, server-side Java and energy efficiency benchmarks. The tests are related to benchmarks that cover typical workloads for enterprise and cloud customers.

Intel also evaluated the impact on online transaction processing (OLTP), estimating it at roughly 4%.

Benchmarks for storage demonstrated a strict dependence on the benchmark, test setup, and system configuration.

For FlexibleIO, which simulates various I/O workloads, throughput performance decreased by 18% when the CPU was stressed, but there was no impact when CPU usage was low.

The tests for FlexibleIO were conducted using different benchmark simulating different types of I/O loads, the results depend on many factors, including read/write mix, block size, drives and CPU utilization.

“For FlexibleIO, a benchmark simulating different types of I/O loads, results depend on many factors, including read/write mix, block size, drives and CPU utilization. When we conducted testing to stress the CPU (100% write case), we saw an 18% decrease in throughput performance because there was not CPU utilization headroom.” continues the analysis. “When we used a 70/30 read/write model, we saw a 2% decrease in throughput performance. When CPU utilization was low (100% read case), as is the case with common storage provisioning, we saw an increase in CPU utilization, but no throughput performance impact.”

The most severe degradation of the performance was observed during Storage Performance Development Kit (SPDK) tests, using iSCSI the degradation reached 25% when only a single core was used. Fortunately, there was no degradation of the performance when SPDK vHost was used.

Intel also reported that Meltdown and Spectre patches are causing more frequent reboots, this behavior was observed for systems running Broadwell, Haswell, Ivy Bridge-, Sandy Bridge-, Skylake-, and Kaby Lake-based platforms.

“We have reproduced these issues internally and are making progress toward identifying the root cause. In parallel, we will be providing beta microcode to vendors for validation by next week,” said Navin Shenoy, executive vice president and general manager of Intel’s Data Center Group.

Only the newest Intel 8th-gen CPUs Coffee Lake seems to be not affected by reboots.

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Pierluigi Paganini

(Security Affairs – Meltdown and Spectre patches, Intel)

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